Kanban Release Action should allow the user to select an existing version

Sometimes, on a Kanban worfklow the team might want to release issues in pre-determined packages, for example: "Customers App - V1.1", "Products App V2.1" ,etc....

Usually these releases are combined with the customer on a periodic basis, so the versions are also pre-determined and the customer will be told something like "your issues 1, 2 and 3 will be released tomorrow, the rest next week". This implies, in this example, two diferent versions.

At this point the Kanban board disregards existing versions when releasing issues from the board. The release action just prompts the user for a version name and overwrites the existing FixVersion field if already set.

I ask for the following behaviour.

• Honor the existing FixVersion on the issues when releasing from the board.
• On the release dialog:
  • Ask for the versions to be released (select distinct fix versions of unrelased issues) on a multi select box. Eg. Versions to release [ Customer-App-v1.1; Orders-App-v2.1; ]
  • optionally ask for the remaining issues (FixVersion isNull) to be released on an existing version or a new one (similar behaviour to the Tags/Labels textbox that exists in jira where the user can pick an existing item or type a new one)