Feat: Session attendance sheet

to be discussed and confirmed with IB/OC/CT

When a user goes to a session he has registered to, allow the option to sign in his/her presence.

To be discussed:

this action could be made by the session's moderator (we would need to create a new role)
It could be done by scanning a QR code (we would need the OC to print them)
We should be able to prevent fraud, users can't register for other absent users
Delegation Leaders should check if their delegation members are attending their registered sessions

uatisdeproblem / egm-app