improve performance of wp mentionable users filter

[ulferts]

Ticket

https://community.openproject.org/wp/61365

What are you trying to accomplish?

Improve the performance of the Queries::Principals::Filters::MentionableOnWorkPackageFilter which is central for returning the users available when trying to mention somebody in a work package comment. On some SaaS instances, the api/v3/principals endpoint using this filter currently has an impact of 50%.

This is caused in part by the filter, when checking for the allowed values fetching the ids of all work packages the requesting user can see.

This is done to validate that the filter is not used for probing for information. While this is necessary to be done, it can be done in a more performant way. Instead of fetching all the ids and then comparing those to the filter's values, the filter can check within the DB that the values are within the visible scope using ARs exists? functionality.

This mechanism should be applied to other HugeList filters as well but this is out of scope for this drive by fix.

[klaustopher]

👏