authors: base record

* Defines fields and models for author base record.

* Adds new function for jsonalchemy models definitions.

* Includes tests for author base record.

Signed-off-by: Mateusz Susik <mateusz.susik@cern.ch>
Reviewed-by: Jiri Kuncar <jiri.kuncar@cern.ch>
oauth2server: fix support of SQLAlchemy-Utils

* Addreses issue with new API of EncryptedType in
  SQLAlchemy-Utils>=0.28.2.  (closes #2629)

Signed-off-by: Jiri Kuncar <jiri.kuncar@cern.ch>