Add test to validate activity field is correctly set.

Problem to solve

We've had some issues with FTS transfers where the user would set the activity flag to some value to get priority over other transfers. In FTS the activity is ok but when the it goes through GFAL somethings goes wrong. Test this functionality in CI to catch regressions in the future.

See: https://gitlab.cern.ch/cta/operations/-/issues/1322

Stakeholders

CTA Team