Follow-up: Extract stack authentication helper into utility

The following discussion from !1814 (merged) should be addressed:

@viktomas started a discussion: (+1 comment)

should this happen at the very beginning of the command? Does it make sense for us to let the user reorder the stack if they are not authenticated?

(Sidenote: I'd expect us to have a helper outside of the stack_reorder.go. do we have an auth code in every command?)