To simplify UI code we are going to expose both Harness API and Standalone API (restricted to harness embedded functionalities) when running in harness mode.
Furthermore, this PR adds a middleware that allows us to reuse standalone Handlers for Harness API for operations that don't require any request/response manipulation.
Adds the following:
- Add GetContent API (with gitrpc, proto, gitadapter changes)
- Add ListCommits API (with gitrpc, proto, gitadapter changes)
- DefaultBranch (to repo table in DB, update branch in git-repo, have default value in config)