Experiment Custom Git Repository

In some cases we need to be able to set a custom Git repository, for instance Github or Gitlab or any other self hosted service.

As a first step; we do not expose any UI for configuring it; the feature is in very early stage.

• PUT /nuxeo/site/studio/v2/project/<project>/remote-repository: to update remote repository properties
• DELETE /nuxeo/site/studio/v2/project/<project>/remote-repository: to remove remote repository configuration

There are some limited identified usages:

• Only Administrators can setup a custom repository
• Github/Gitlab protected branch are handled for now as a "merge issue"; without any proper informative message asking the user to do a PR from the remote system.
• Gitlab doesn't create a repository with a default master branch, and it has to be created manually first from Gitlab
• You need to git clone --mirror your Studio repository first.
• Using external system will not hide at all wip-* branches
• Moving a tag doesn't override release, neither trigger a release build.
• We do not cover, for now, any side effect from unexpected results tied to force pushes, ...