Type annotations for utils

[jderuiter]

Added type annotations to bookwyrm.utils. In isni.py I changed some code to handle the case when ET.Element.find or ET.Element.text might return None. I left two TODOs in the code where there is still some decision to make to either return nothing or raise an exception.

[mouse-reeve]

I'm not sure how to best resolve the conflicts on base_activity here

[hughrun]

@jderuiter as far as I can tell the conflicts are all with your work from last week so I'm also not sure whether the intention is to replace that work or build on it. Is it possible for you to rebase your mypy-utils on top of the current main? I think that should resolve these merge conflicts.

[jderuiter]

Thanks for looking at this. This PR is actually older than last week's so probably those changes should take precedence. I'll have a look at it and fix this PR. It might take a couple of weeks before I have time for this.

[jderuiter]

The conflicts should have been resolved now.

[dato]

I was just reading along and noticed these two things, in case they're useful.

[hughrun]

Looks pretty good to me other than as noted. Thanks for those improvements to the isni code.