Make epic link selector pull from epics search API

[mickmister]

At the moment, we are using JQL directly to fetch epic links for a given project. This is resulting in inconsistent behavior between Mattermost's epic selector and Jira's.

https://github.com/mattermost/mattermost-plugin-jira/blob/17e8a47f8a644f853383301e6129ee940d715942/webapp/src/components/data_selectors/jira_epic_selector/jira_epic_selector.tsx#L79

We can instead use the autocomplete endpoint for a project's epic links: https://myorg.atlassian.net/rest/agile/1.0/epic/search?excludeDone=true&projectKey=CLD&maxResults=20&query=

One known limitation to the current implementation is that the epic links must be a member of the same project as selected in the MM form. Jira's epic link selector allows for epics from other projects, so that functionality should be tested with this feature.

[Jenis07]

Can you assign me this issue?

[mickmister]

Absolutely :+1: Thanks @Jenis07!!

[mickmister]

Hi @Jenis07, just checking in. Do you have any questions about this issue? Thank you!