Unavailable dates should prevent new assignments from going to editors
Currently, if a user account is marked as "unavailable" for a period of time, it only affects their ability to receive review assignments. For the Editor-in-Chief, this means new assignments can keep being sent to unavailable editors. Simply adding "N/A" to the name in the drop-down list is not going to prevent the editor from actually making the assignment. If an editor's account is marked as "unavailable," they should be omitted from the list of potential editors during those dates. (This would effectively be a temporary "soft end date" for their AE role.)
