[Feature][GitLab] Add assignees and reviewers to table.pull_requests

[Startrekzky]

Search before asking

• I had searched in the issues and found no similar feature requirement.

Use case

I want to analyze the assignees and reviewers of GitLab MRs, so I want to add certain fields to the pull_requests table.

Description

There're a few things to do:

• Add two tables pull_request_reviewers and pull_request_assignees to the domain layer pull_requests table.
• Add reviewers and assignees to the tool layer GitLab merge requests table (It doesn't have to be two tables).
• Extract and convert reviewers and assignees from the raw layer of GitLab MRs to the tool and domain layer.

Related issues

No response

Are you willing to submit a PR?

• Yes I am willing to submit a PR!

Code of Conduct

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