feat: Add Integration Tests and CI Workflow for Unit Tests

Introduced IntegrationTestFactory.cs as a foundational class to configure integration tests.
Added DatabaseTest class as a helper containing useful and reusable methods and dependencies for testing.
Implemented ServiceCollectionExtensions to streamline service registration in tests.
Started implementing WorkoutControllerTests and WorkoutPlanControllerTests to validate controller functionality.
Introduced wf-tests.yml for the CI workflow to automate the execution of unit tests.
Added Resource class to store 201 status code data.

makampos / fit-sync