Allow project path in MergeRequestFilter

[mhagnumdw]

Currently, the MergeRequestFilter requires the project ID (number) to filter merge requests. It would be very useful to allow passing the project path (e.g., group/subgroup/project) directly in the filter, since retrieving the project ID often requires an extra API call.

try (GitLabApi gitLabApi = new GitLabApi(url, token)) {
    MergeRequestFilter filter = new MergeRequestFilter()
        .withSourceBranch(sourceBranch)
        .withTargetBranch(targetBranch)
        .withState(MergeRequestState.OPENED)
        .withProjectId(gitLabApi.getProjectApi().getProject(projectPath).getId()) // extra API call here
     // .withProjectIdOrPath(projectPath) // something like this
        ;
    List<MergeRequest> mergeRequests = gitLabApi.getMergeRequestApi().getMergeRequests(filter);
}

Alternatively, it would also help to provide an overloaded version of the method
public List<MergeRequest> getMergeRequests(Object projectIdOrPath) throws GitLabApiException
that accepts a MergeRequestFilter as a parameter.

[jmini]

I see the point, in the docs:
https://docs.gitlab.com/api/merge_requests/#list-project-merge-requests

:id is integer or string

So yes I agree that your request makes sense.

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Maybe the second variant with the dedicated method would be more consistent with the other methods provided by gitlab4j.

In this case we would just make sure that withProjectId(..) is not used in the filter.

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Do you want to contribute a pull-request?