refactor: Project onboarding workflow

[zmotso]

Pull Request Template

Description

• Refactored put_project.go to improve code maintainability
  • Extracted error handling into reusable handleError helper method
  • Consolidated git provider initialization throughout the code
  • Simplified push operation to use a single call with multiple refspecs
  • Improved error messages with more context
• Rewrote tests in put_project_test.go with better coverage
  • Split tests into separate files for third-party Git providers and Gerrit
  • Added comprehensive test cases for success and error scenarios
  • Reduced test complexity and improved maintainability
• Enhanced GitServer API documentation
  • Added detailed description for nameSshKeySecret field
  • Documented required and optional secret keys for each Git provider
• Move Git package from v2 to the main pkg directory
  • Updated import paths across the codebase
  • Removed deprecated package files

Fixes #231

Type of change

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

How Has This Been Tested?

• Unit tests
• Manually

Checklist:

• I have performed a self-review of my code
• I have commented on 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
• Pull Request contains one commit. I squash my commits.