Author filter fails to populate when user has a large volume of todos

Summary

The author filter searches through the list of todos to get a filterable list of authors. When there are a large number of todos to sort through, this request can time out and make the autocomplete inoperable.

original comment

Steps to reproduce

Note: This is a timeout issue and is difficult to reproduce naturally.

1. Have a large number of TODOs or block/throttle the /-/autocomplete/users.json endpoint.
2. Try to filter by author

What is the current bug behavior?

The request times out and the message, "No suggestions found" is shown

What is the expected correct behavior?

We see a list of usernames. Either the request completes, or we fall back to the standard list of users.

Relevant logs and/or screenshots

original comment

Possible fixes

There are two paths we can take to solve this. Making the endpoint faster, and having a more useful fallback. We should take at least one of these and consider taking both