Add support for keyset pagination in RepositoryClient

[msrouchou]

• As the title says, implement the keyset pagination support
• https://docs.gitlab.com/ee/api/repositories.html#list-repository-tree:~:text=with%20keyset%20pagination.-,pagination,-string
• As the comment says, This endpoint changed to keyset-based pagination in GitLab 15.0. Iterating pages of results with a number (?page=2) is unsupported.

[jairbubbles]

Thinking of pagination, it's a mess right now, it is not supported on all APIs. Maybe we could at the same time rethink how it's done?

[meziantou]

On other endpoints, NGitLab enables keyset pagination transparently if the parameters are ok. For instance,

NGitLab/NGitLab/Impl/ProjectClient.cs

Line 78 in 5d4b6da

url = Utils.AddOrderBy(url, query.OrderBy, supportKeysetPagination: SupportKeysetPagination(query));

. I think we can do the same for this endpoint.

[jairbubbles]

My problem was on the project commits API, there were no way to specify it. Hopefully it was already set to max page size.

[msrouchou]

Just an FYI, when I created this issue, it was because I needed to get specific files knowing their extensions in GitLab.
I discovered that you can use the search endpoint instead, which has a less known syntax.

Example, I could just search for the file extensions I needed by calling

/api/v4/projects/{id}/search?scope=blobs&search=extension:csproj

you can also search by filename, path, etc https://docs.gitlab.com/ee/user/search/advanced_search.html#code-search

I still cannot get over it, it made my life easier on so many levels 😆