Automatically subscribe user to study group when user attends to session (study_group_presence log)

[danicuki]

When the user attends to a study group, it is created in the database a log of the user presence.

The log has the user discord_id.

We must create a function that monitors study_group_presence creation. When the log is created, it looks in the users collection for someone with the same discord_id as the one logged. If the user is found, adds the study_group_id to the study_group_ids list in the user's object in firestore