As a user, I want to assign an issue to a specific sprint, (like I can assign it to a fix version), such that the issue is planned

Check discussion on AAC
https://answers.atlassian.com/questions/104490/how-to-assign-an-issue-to-a-greenhopper-sprint/104867

When you are looking at an issue (not in the context of the planning board), you should be able to indicate in what sprint you want this issue to be done. This is typical when you encounter the issue while triaging, and you know that you are going to address similar issues in a future sprint.

Also related to GHS-4949