Add can_create_merge_request_in to Project API response
Add a can_create_merge_request_in
attribute to a show project API response.
These four issues (%12.8 & %12.9) all share the same core problem that the Web IDE FE needs to know if the current user can create a merge request on the current project.
@rkuba notes that "I would expect there is information available on the backend telling the IDE right away that MRs are not available. So at least we should be able to pass down a flag to the IDE and disable the MR experience." which is similarly the case for !35715 (closed) where we prompt to fork if pushing to the project is disabled but MR is enabled.
This merge request permission information via GraphQL at the moment, but not API.
The above four issues all depend on this one.