feat: Add GitLab support with configuration, client, and API actions

[rostilos]

This pull request introduces initial support for GitLab as a VCS provider across the codebase, including configuration, DTOs, client libraries, and database migrations. It also adds a new repository-scoped token connection type, improves branch statistics calculation, and enhances project DTOs with webhook configuration status. The most important changes are grouped below:

GitLab Integration Support:

• Added GitLabConfig record and serialization support for GitLab connections, including self-hosted instances, to VcsConnectionConfig and related modules. [1] [2] [3] [4]
• Introduced GitLabDTO for representing GitLab VCS connections and exporting the DTO in the module. [1] [2]
• Added configuration instructions and properties for GitLab OAuth integration in application.properties.sample.
• Implemented GitLabClient and related exports in the VCS client library, and enabled the VcsClientFactory to create GitLab clients. [1] [2] [3] [4]
• Added an OkHttpClient factory method for GitLab API authentication.

Database and Model Changes:

• Added GITLAB to the allowed values in the vcs_connection.provider_type database constraint.
• Added a repositoryPath field to VcsConnection for repository-scoped token support, with corresponding getters and setters. [1] [2]
• Added a migration to remove the deprecated FORGE_APP connection type and introduce REPOSITORY_TOKEN as a new connection type in the database.

Repository Token Connection Type:

• Updated EVcsConnectionType enum to add REPOSITORY_TOKEN and clarified connection type comments.

Project and Branch DTO Enhancements:

• Extended ProjectDTO to include a webhooksConfigured field, populated from the VcsRepoBinding. [1] [2] [3]
• Improved branch statistics calculation to derive counts directly from the issues list for accuracy.

Miscellaneous:

• Added a migration to backfill missing commit_hash values in code_analysis from the associated pull requests.

[coderabbitai]

Important

Review skipped

Auto reviews are disabled on base/target branches other than the default branch.

Please check the settings in the CodeRabbit UI or the .coderabbit.yaml file in this repository. To trigger a single review, invoke the @coderabbitai review command.

You can disable this status message by setting the reviews.review_status to false in the CodeRabbit configuration file.

---

_{Comment @coderabbitai help to get the list of available commands and usage tips.}