[FEATURE] - Implement Smart Matrix CI Workflow

[Ofido]

Is your feature request related to a problem?

The current CI workflow runs the same set of tests for every trigger, which is inefficient. We need a more robust setup that ensures compatibility across different environments without wasting GitHub Actions minutes on every single push.

Describe the solution you'd like

Implement a smarter CI strategy in .github/workflows/ci.yml with two distinct execution policies:

1. Fast Feedback (on pushes to feature branches):

   • Trigger: on: push, excluding the main branch.
   • Action: Run the test suite on a single, fast configuration (e.g., Python 3.12 on ubuntu-latest).
   • Goal: Provide quick validation to developers with minimal resource consumption.

2. Comprehensive Validation (on pull requests to main):

   • Trigger: on: pull_request, when the base branch is main.
   • Action: Run the full test matrix across:
     • Operating Systems: ubuntu-latest, windows-latest, macos-latest.
     • Python Versions: 3.9, 3.10, 3.11, 3.12.
   • Goal: Ensure maximum compatibility and stability before merging into the main branch.

Describe alternatives you've considered

• Running the full matrix on every push (too expensive and slow).
• Not running a matrix at all (risks undiscovered compatibility issues).

Additional context

This is from the DevOps and CI/CD section of the roadmap.