[Squad-dev] squad 1.16 release

Hi,

This 1.16 release improves load time when comparing tests across different projects, creates a default authentication group so that users have object-level permission and allows download of build attachments.

Complete list of changes going in:

* frontend: * add URL for downloading build attachments * add test history link in test list * allow serving files from database * compare: improve compare load times * fix attachment downloads * test the actual response contents of all download urls * add migrations to create auth group and add users * api: rest: add more status details * attachment: add a sample unit test * core: store Attachment's mime-type in the model * pytest: only check coverage on ci

Ch{eers,arles}