[16.0][ADD] website_event_private: new module

[Hugo-Trentesaux]

This is an update on PR #385 with a bugfix.

This module allows to select privacy on event and generate an access link for private events to be shared with foreseen attendees

This module is used in production in two instances.

[github-actions]

There hasn't been any activity on this pull request in the past 4 months, so it has been marked as stale and it will be closed automatically if no further activity occurs in the next 30 days.
If you want this PR to never become stale, please ask a PSC member to apply the "no stale" label.

[Hugo-Trentesaux]

Not stale, just missing reviewer. And it could help some tests.

[github-actions]

There hasn't been any activity on this pull request in the past 4 months, so it has been marked as stale and it will be closed automatically if no further activity occurs in the next 30 days.
If you want this PR to never become stale, please ask a PSC member to apply the "no stale" label.

[Hugo-Trentesaux]

Not stale, just missing reviewer.