We don't need to connect when requesting the name of the database
adapter. This in turn should prevent us from requesting/leaking
connections just by asking whether we're using PostgreSQL or MySQL.
When I proposed using serializable transactions I was hoping we would be
able to refresh data of individual users concurrently. Unfortunately
upon closer inspection it was revealed this was not the case. This could
result in a lot of queries failing due to serialization errors,
overloading the database in the process (given enough workers trying to
update the target table).
To work around this we're now using a Redis lease that is cancelled upon
completion. This ensures we can update the data of different users
concurrently without overloading the database.
The code will try to obtain the lease until it succeeds, waiting at
least 1 second between retries. This is necessary as we may otherwise
end up _not_ updating the data which is not an option.
When using #XYZ in Markdown text, if XYZ exceeds the maximum value of a signed 32-bit integer, we
get an exception when the Markdown render attempts to run `where(iids: XYZ)`. Introduce a method
that will throw out out-of-bounds values.
Closes#18777
