Select/remove epic from Epic section in sidebar

Design solution

Requirements Let's reuse the Milestone dropdown design and interactions for this MVC.

• A. User can add the Epic from within the issue, in the sidebar.
• B. User is able to click on edit within the Epic area in the sidebar to access the Assign Epic dropdown.
  • User can click on an Epic to associate it with the issue.
  • User can click on the checked Epic again to deselect and dissociate it with the issue. They may also select "No Epic". This is consistent with the Assign Milestone dropdown.
  • The dropdown should show epics from this group and from parent groups, the same as the milestone and label dropdowns do.
• C. User can type the Epic title to get the Epic returned in their search.
• D. User can type the Epic number to get the Epic returned in their search.
• E. User can type the Epic link to get the Epic returned in their search.
• For MVC, wrap applied Epic titles in the sidebar as we do already.

Usability Polish

• The text falling underneath the icon here doesn't seem like a great experience. Can we prevent this? I added some right padding to the input box to get something more in line with what I would expect (do whatever you feel is best to recreate!):

• Long Epic titles can behave the same as long Milestone titles for MVC. I would love if we could truncate after around 25 characters, but that can be stretch. I am expecting this to be something we will need to improve in the next iteration and as we work on the dropdown component.

Archive of @smcgivern 's comments

• From within an issue.
• Add an epic to it by selecting one via a dropdown menu.
• Dropdown menu should have the ability to search and browse epics, or should take an epic number or link
• Remove the association from the epic by removing it. Click a remove link in the issue sidebar itself.
• The dropdown should show epics from this group and from parent groups, the same as the milestone and label dropdowns do.