RATIONALE

Event will soon gain a major update called Event Online, allowing to better
support full-online events. In order to prepare its merge, preparatory merge
are done to lessen the final diff and have a smooth integration in a stable
version (13.3).

PURPOSE

Purpose of this merge is to clean visitor synchronization and tests. It
prepares further improvements to visitor model linked to Event Online.

SPECIFICATIONS

Make tests independent from existing database data, notably existing visitors.
Use newly-introduced tools and data. Clean tests and make them easier to
understand, notably connection / disconnection effects. Make more tests about
visitor data: name, partner_id, tracks move from visitor to authenticatedf
visitor, ...

LINKS

Task ID 2290016 (improve visitor synchronization and tests)
Prepares Task ID 2252655 (main Online Event task)
Prepares Task ID 2284043 (Visitor-based track wishlist)
PR #54036

X-original-commit: 015f70dd1ce1394d279f8fbb949948f4845c65fc