Race condition in \Drupal\content_lock\ContentLock\ContentLock::locking() as we fetch the lock (select) and then separately create the lock (merge)

We can't do the merge idea because merge is implemented as a select and update or insert... so yet another opportunity for races... so we can consider using upsert or using the lock system.

Wasn't sure how to trigger the lock but applying the MR on the site we are using on and locks still appear to be working just fine. So going to lean on that.

I've tried to write a test for this - both low level and and high level - using pcntl_fork() to simultaneously lock via the API and UI neither worked because it is hard to have multiple sessions as the same time in FunctionalTests and separate service instances in kernel tests.

Automatically closed - issue fixed for 2 weeks with no activity.