feat: Unify repository endpoints and add multi-provider support

[zmotso]

Pull Request

Description

• Replace provider-specific endpoints with generic /api/v1/repositories and /api/v1/repository endpoints in the OpenAPI spec
• Move all parameters to query params instead of path params for a simpler, unified API
• Remove provider-specific handlers (GitHub, GitLab, Bitbucket) and use a single RepositoryHandler

Fixes #15

Type of change

Please delete options that are not relevant.

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• This change requires a documentation update

How Has This Been Tested?

• Manually

Checklist:

• My code follows the style guidelines of this project
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• My changes generate no new warnings
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes
• Any dependent changes have been merged and published in downstream modules
• I have squashed my commits