Suggest available Jira issues when editing a Merge Request title or description
## Problem to solve Having the ability to quickly select from a list of Jira issues when editing a MR title or description would be a nice QOL improvement. ## Related issues This issue is part of epic to improve the Jira <> Merge Request experience &4637. Related issues and suggested order of implementation: 1. Add a project-level toggle to require Jira association in Merge Requests gitlab#268294 1. Add Jira ticket association requirement to Merge Requests gitlab#268292 1. Add a project-level toggle to require Jira association in Merge Requests gitlab#268294 1. This issue ## Proposal 1. When the feature flag is enabled. 1. And the project has Jira integration. 1. When a user types in text that matches the an integrated Jira project's code, for example `JRE`. 1. Then show an autocomplete dropdown with the Jira ticket numbers and titles. 1. When a user types in text that matches the start of a Jira ticket, for example `JRE-11`. 1. Then show an autocomplete dropdown with the Jira tickets that match the entered text, for example `JRE-110, JRE-111`. 1. When a user clicks on a suggestion, insert the Jira ticket reference into the textfield. A note on Jira ticket formatting. The ticket reference is always in all caps, contains a dash and ends in a number. ![Autofill](https://gitlab.com/gitlab-org/gitlab/uploads/4657d865ea8cf4f2b2199ec674bae5de/Autofill.png) ## Implementation issues 1. ~backend https://gitlab.com/gitlab-org/gitlab/-/issues/352498 2. ~frontend https://gitlab.com/gitlab-org/gitlab/-/issues/352497
epic