fix: standarize errors in events context

lib/bokken/events.ex

@@ -623,7 +623,7 @@ defmodule Bokken.Events do
     if DateTime.compare(event.enrollments_open, cur_time) == :lt and
          DateTime.compare(event.enrollments_close, cur_time) == :gt do
       if is_ninja_enrolled?(ninja_id, event.id) do
-        {:error, :ninja_already_enrolled}
+        {:error, :already_enrolled}
       else
         insert_enrollment(role, attrs)
       end
@@ -713,7 +713,7 @@ defmodule Bokken.Events do
     if DateTime.compare(event.start_time, cur_time) == :gt do
       Repo.delete(enrollment)
     else
-      {:error, "Cannot delete enrollment of past session"}
+      {:error, :not_authorized}
     end
   end
 
@@ -851,14 +851,14 @@ defmodule Bokken.Events do
     if DateTime.compare(event.enrollments_open, current_time) == :lt and
          DateTime.compare(event.enrollments_close, current_time) == :gt do
       if mentor_availability_exists?(mentor_id, event.id) do
-        {:error, "Mentor has already stated availability for this event"}
+        {:error, :already_enrolled}
       else
         %Availability{}
         |> Availability.changeset(attrs)
         |> Repo.insert()
       end
     else
-      {:error, "Availability cannot be created when event enrollments are closed"}
+      {:error, :enrollments_closed}
     end
   end
 

lib/bokken/guards.ex

@@ -28,13 +28,11 @@ defmodule Bokken.Guards do
 
   """
   defguard is_404(reason) when reason in [:not_found, :not_registered, :invalid_credentials]
-  defguard is_401(reason) when reason in [:token_expired]
+  defguard is_401(reason) when reason in [:not_authorized, :token_expired]
 
   defguard is_403(reason)
            when reason in [
-                  :not_authorized,
-                  :not_allowed,
-                  :ninja_already_enrolled,
+                  :already_enrolled,
                   :enrollments_closed
                 ]
 end