Group Level Wiki: BE Support Git access for Group Wikis

Problem to solve

Group wiki repositories need to be accessible through Git over HTTP and SSH.

Note: This issue is a child of the Group Level Wiki Implementation Epic &2214 (closed)

Proposal

Add all necessary Git routes, similar to the changes in !21739 (merged) :

• The controllers in app/controllers/repositories are used for HTTP access.
• The allowed endpoint in lib/api/internal/base.rb is used for SSH access (through gitlab-shell).

LFS support is out of scope for this issue, and will be addressed with #271569.

Permissions and Security

Use the permissions established in #207872 (closed).

Documentation (remove if not applicable)

Update https://docs.gitlab.com/ee/user/group/index.html#group-wikis-limitations

Success Criteria

• Group wiki repositories can be accessed over HTTP (clone/push)
• Group wiki repositories can be accessed over SSH (clone/push)