Allow users to attend a training
Don't allow a user to attend a session that overlaps with another already attending
Merge branch 'develop' into feature/attend-training
Rebase migration
Move attending / leaving a session logic into model
Rename "unattend" to "leave"
Add training export on badge
Cleanup
Merge branch 'develop' into feature/attend-training
Add missing file
Add session-attendances view.
Rename profile.trainings to profile.sessions_attending
Fix test fixture
Merge pull request #159 from EuroPython/feature/attend-training

Allow attendees to formally attend a training