Deploy applications from private github / gitlab

[richard-cox]

Create

• Add a new source types when deploying an application
  • Private Github
  • Private Gitlab
• Ask the user to select a credential that is of type private github / private gitlab
• Not sure of how the api requests work, but this must be supplied when creating the app

Edit

• Users should be able to change the credentials associated with an app

Generally

• When viewing source information for an application deployed by this type ensure that we proxy the information via the backend (see Proxy github / gitlab requests via epinio backend #329 )