Consider exit_function decorator

We may want to have `exit_function` as a decorator. This would allow us to add something like `@exit_function` above any function definition that we want to use this for without having to explicitly update the function at all.

May be worth exploring in the future.

_Originally posted by @dr-rodriguez in https://github.com/astrodbtoolkit/astrodb_utils/pull/152#discussion_r2098867964_

Start by reviewing the existing `exit_function` implementation and the discussion in pull request #152. Determine the decorator’s intended behavior, how it should apply to function definitions, and which existing uses would need to change. Done means the design is agreed and the relevant behavior is covered by tests.

Written by the indexing model from the issue text.