docs(history): add documentation on some management commands

[sennierer]

resolves #873

[koeaw]

Could there be a 1-sentence or half sentence explanation about duplicates added?

Why are there duplicates/how do they come about/why do they need cleaning? Or alternatively a link to where the django-simple-history docs talk about them.

[sennierer]

I dont think that there is an answer to this. Depending on your code you might call save on an object twice (eg via signals) and get duplicates. This management command just checks whether there are exactly the same objects in your history tables and removed one.

[koeaw]

All of the commands mentioned feature the argument --auto, but its purpose is never explained.

Would add a note either to the description of the first command (first appearance) or here at the end – or leave if off altogether (if possible/sensible).

[sennierer]

Ran the whole part of the documentation through an LLM to improve writing and structure.