Reintroduce BaseContractTest class that was not migrated from Odoo 14

[AlexandrePhilibert]

Reintroduce the BaseContractTest class that is required for the new donor onboarding tours test.

[greptile-apps]

Confidence Score: 5/5

The restored fixture is compatible with the current downstream consumer hierarchy and is safe to merge.

No defects remain after the executed downstream compatibility check disproved the only failure hypothesis. Odoo runtime execution is unavailable locally, but the changed fixture API and its active cross-repository use were directly checked.

Files Needing Attention: No files need changes. An Odoo-provisioned environment can additionally run the addon test suite when available.

T-Rex Logs

What T-Rex did

• The base contract validation script was executed and exited with RESULT=PASS, confirming the inheritance chain does not rely on fixture members omitted from this restoration.
• A broader Python validation was attempted by compiling tests and importing Odoo; the compile completed but the runtime import failed with ModuleNotFoundError: No module named 'odoo' because Odoo is not installed in this environment.
• Related artifacts documenting the contract validation and Odoo-import attempt were collected and archived to support review.

_{Ran code and verified through T-Rex}

_{Reviews (1): Last reviewed commit: "FEAT: Reintroduce BaseContractTest class..." | Re-trigger Greptile}