## Description https://gitlab.com/gitlab-org/gitlab/-/issues/427437 solves the problem for interacting with users quickly in plain text editor. We should have this improvement in the rich text editor. ### Proposal Solve this problem for rich text editor in the same way under the same feature flag, for issues and MRs. MR for plain text suggestions: https://gitlab.com/gitlab-org/gitlab/-/merge_requests/139085 ## Context from https://gitlab.com/gitlab-org/gitlab/-/issues/427437: ### Problem to solve Currently, you need to wait a few seconds the first time you interact with the users dropdown (or quick actions). ### Proposal We can pass the `search` param to the backend autocomplete endpoint to only return results based on what user typed, with a limit of 20. **This change should be behind a feature flag gated by current_user.**