WebAPIKey: initial Flask port

• Moves web_api_key logic to the model.

• Refactors functions to work with sqlalchemy and flask request.

• Refactors web_api_key to work with model functions.

• Updates web_api_key_regression_tests.

Signed-off-by: Konstantinos Ntemagkos <konstantinos.ntemagkos@cern.ch>
Reviewed-by: Jiri Kuncar <jiri.kuncar@cern.ch>