[V2] Officially support authenticated sessions and allow to perform certain actions on them.

[LoicPoullain]

Issue

Resolves #510.
Resolves #778.
Resolves #779.

Solution and steps

• Use an object argument in the Session constructor for better readability.
• Add an optional field userId to Session.
• Make all the three stores use Session.userId when saving and reading the session (and updating from redis).
• Make @TokenRequired use Session.userId to authenticate the session.
• Add TypeORMStore.getAuthenticatedUserIds()
• Add TypeORMStore.destroyAllSessionsOf(user)
• Add TypeORMStore.getSessionsOf(user)

Breaking changes

• Interface of the Session constructor.
• TypeORMStore only support numbers (not strings) as user IDs.
• The userId is not stored in the session content.
• Redis session key now starts with sessions: instead of session:.
• MongoDB collection is now named sessions instead of foalSessions.

When migrating to v2, all users will be logged out.

When migrating to v2 (optional) :

• remove the old TypeORM table,
• remove the old MongoDB foalSessions collection.

Checklist

• Add/update/check docs (code comments and docs/ folder).
• Add/update/check tests.
• Update/check the cli generators.