Add ADR to select an authentication approach

docs/architecture-decisions/0005-use-cancancan-for-authorization.md → docs/architecture-decisions/0006-use-cancancan-for-authorization.md

@@ -1,4 +1,4 @@
-# 5. Use CanCanCan for authorization
+# 6. Use CanCanCan for authorization
 
 Date: 2024-06-25
 
@@ -11,17 +11,17 @@ Accepted
 We will need authorization in TACOS to support the staff user interface. Specifically, we will need to manage access
 to the following features:
 
-* The categorization interface. This is one of the core features of TACOS, in which staff will match logged search
-terms to categories.
-* The 'Hints' system. TACOS will provide a dashboard to manage Hints, which are currently maintained in a Google
-spreadsheet.
-* Reporting dashboard. Initially, TACOS will provide monthly statistics on matched algorithms. We will likely add
-more reporting functionality in the future.
+- The categorization interface. This is one of the core features of TACOS, in which staff will match logged search
+  terms to categories.
+- The 'Hints' system. TACOS will provide a dashboard to manage Hints, which are currently maintained in a Google
+  spreadsheet.
+- Reporting dashboard. Initially, TACOS will provide monthly statistics on matched algorithms. We will likely add
+  more reporting functionality in the future.
 
 The authorization gem we select should also be able to support features beyond those listed above, as we are not sure
 what TACOS might become in the future.
 
-## Options considered 
+## Options considered
 
 For the purpose of this ADR, I considered three popular authorization gems. These are not the only available options,
 but they are widely adopted and well supported.
@@ -53,11 +53,11 @@ for a more detailed example.)
 
 Pundit also allows for more granular access control via
 [scopes](https://github.com/varvet/pundit?tab=readme-ov-file#scopes). This feature is the most compelling reason to
-choose Pundit over CanCanCan, but it's unclear whether we would need it in this application. 
+choose Pundit over CanCanCan, but it's unclear whether we would need it in this application.
 
 Because it requires a separate policy class per model, Pundit can require some repetitive code if authorization
 policies are similar across multiple models. We might be able to mitigate this by abstracting common logic to the
-`ApplicationPolicy` from which all policy classes inherit. 
+`ApplicationPolicy` from which all policy classes inherit.
 
 ### Action Policy
 

docs/architecture-decisions/0007-use-devise-for-authentication.md

@@ -0,0 +1,104 @@
+# 7. Use Devise for authentication
+
+Date: 2024-07-11
+
+## Status
+
+Accepted
+
+## Context
+
+We will need to authenticate users in TACOS to help manage access to the staff interface. The ideal authentication
+approach would involve Omniauth integration, as IS&T recently implemented Okta, and
+[a strategy exists](https://github.com/omniauth/omniauth_openid_connect) to authenticate with OIDC using Omniauth.
+
+## Options considered
+
+### [Devise](https://github.com/heartcombo/devise)
+
+Devise is the far and away the most popular authentication gem, and the one with which we have the greatest familiarity.
+It is well-documented and feature-rich, and it integrates seamlessly with Omniauth, which we will likely use to work
+with Okta.
+
+Devise is also something of a black box, and its extensibility causes a steep learning curve. All of us in EngX have
+worked with Devise, but not all of us have configured it from scratch in a new application. As a result, our collective
+understanding of how the gem works is fairly limited.
+
+We also anticipate fairly straightforward authentication needs for this application, so its extensibility may just add
+complexity and not value.
+
+### [Sorcery](https://github.com/Sorcery/sorcery)
+
+Sorcery positions itself as a simpler alternative to Devise. It uses only 20 public methods, which follow familiar
+conventions (e.g., `current_user` and `logged_in?`). Though other gems also strive for simplicity (see Clearance,
+below), Sorcery seems to be most successful in this.
+[Some have switched to it from Clearance](https://github.com/Sorcery/sorcery/issues/248#issuecomment-1306195246) for
+this reason.
+
+The downside of simplicity is it does not include features we'd need, such as
+[integration with Omniauth](https://github.com/omniauth/omniauth/issues/1042). Some customization would be required.
+I've not yet found a sample implementation with Omniauth, so we might need to figure it out on our own. It's also
+notable that Sorcery is not yet in v1, and he have struggled at times to keep up with changes in pre-major-release
+gems (Administrate is the first example that comes to mind).
+
+### [Clearance](https://github.com/thoughtbot/clearance)
+
+Clearance is another popular option. Like Sorcery, it offers a simpler approach than Devise. It's opinionated, which
+makes for quicker setup, but it also claims to make it easy to override defaults. Anecdotally, this claim
+[appears to be true](https://everydayrails.com/2016/01/23/clearance-rails-authentication#sensible-defaults), but the
+defaults would likely be sufficient for us.
+
+Also like Sorcery, Clearance has no Omniauth integration. [This gist](https://gist.github.com/stevebourne/2394427) gives
+a sense of what might be required to build out that feature.
+
+Clearance seems to be less ubiquitous than Sorcery, but more regularly maintained. Despite the lower adoption rate,
+Clearance appears to have a very helpful user community, as demonstrated by the gist shared above.
+
+### [Authlogic](https://github.com/binarylogic/authlogic)
+
+Authlogic is a highly customizable authentication solution, and with more than 10 million downloads on RubyGems, it
+appears to be the second most popular option after Devise. However, because it is so customizable, it has a steeper
+learning curve than some of the alternatives. It is also less actively maintained, with no releases so far this year
+and only 3 since 2021.
+
+### Custom solution
+
+We could build out our own authentication code. [Here is an example](https://stevepolito.design/blog/rails-authentication-from-scratch)
+of this approach, and another [Omniauth-specific example](https://github.com/omniauth/omniauth?tab=readme-ov-file#rails-without-devise).
+
+This approach would reduce our reliance on dependencies, and it may help us understand our application better. Many
+authentication gems use a fair amount of magic to make them easier to implement, but this can also make it difficult
+to understand how they work.
+
+However, this approach would also introduce the signfiicant risk of writing and maintaining our own authentication code.
+We might consider the [Authentication Zero](https://github.com/lazaronixon/authentication-zero) to generate the initial
+code, which would significantly speed up implementation, but maintenance would still become our responsibility. If we
+use a preexisting gem, we are effectively delegating that responsibility to others that presumably have more expertise
+in this space.
+
+## Decision
+
+We will use Devise for authentication. Despite its complexity and opacity, Devise is the most popular authentication gem
+by a wide margin. We already have some familiarity with it, and we use it in our other applications. While we will not
+need the vast majority of its features, we likely will use the Omniauth integration, which will save us from writing
+some additional code.
+
+Sorcery and Clearance are compelling due to their ease of use. However, they may end up being _more_ complex to
+implement due to their lack of Omniauth integration.
+
+Authlogic feels equally complex as Devise, albeit more transparent. It also seems not to be especially well maintained.
+
+A custom solution would be an interesting way leverage built-in Rails functionality while reducing our reliance on
+third-party libraries. However, it is difficult to justify considering the additional risk and development time.
+
+Ultimately, while all of these alternatives are appealing, there is a distinct advantage to choosing a gem that "just
+works" and is widely adopted. Much like our
+[decision to use CanCanCan for authorization](https://github.com/MITLibraries/tacos/blob/main/docs/architecture-decisions/0006-use-cancancan-for-authorization.md), I might not feel like Devise is the best authentication gem, but I have
+a difficult time convincing myself not to use it for this project.
+
+## Consequences
+
+To choose Devise is to double-down on a gem that is a black box. Whether we build our own solution or adopt a more
+streamlined gem, there is an opportunity to gain a greater understanding of this critical feature, and possibly
+even build expertise in Rails security. This decision effectively sacrifices that opportunity for the sake of
+convenience.