Add pagination to user following/follower lists

[pidgezero-one]

Closes #9283

Adds pagination support to people/:username/followers and people/:username/following

Technical

• I added results_per_page as a mandatory variable in the template instead of optional, so that the page size given to the macro will always match the page size used for calculating the offset in the DB query
• An easier way to solve this issue would have just been to pass a slice of follows to the template, but I don't think returning the whole DB contents would be solving an issue of performance as well as returning a constant 25 or fewer rows does.
• I added limits and offsets to the methods in core/follows.py, but I made these params optional so as to not break other parts of the code that use get_following. I looked in other parts of the codebase to verify that None and 0 are appropriate defaults.
• Also removed some unused imports and replaced some spacing in the HTML file that was loading weirdly in my code editor

Testing

I inserted dummy data into the follows table to verify that both lists loaded correctly at 0, 1-25, and 26+ entries, and verified that the pagination UI loads the correct section of the list depending on the page (http://localhost:8080/people/openlibrary/followers, http://localhost:8080/people/openlibrary/followers?page=1, http://localhost:8080/people/openlibrary/followers?page=2).

Screenshot

These are zoomed out.

Following list, 25 entries in total:

Following list, 26 entries:

Following list, empty:

Followers list, 25 entries in total:

Followers list, 26 entries:

Followers list, empty:

Stakeholders

@mekarpeles

Attribution Disclaimer: By proposing this pull request, I affirm to have made a best-effort and exercised my discretion to make sure relevant sections of this code which substantially leverage code suggestions, code generation, or code snippets from sources (e.g. Stack Overflow, GitHub) have been annotated with basic attribution so reviewers & contributors may have confidence and access to the correct context to evaluate and use this code.

[mekarpeles]

This is a great start @pidgezero-one, great work so far.

You might consider running it using gitpod which may also give you some more detail about anything that may be going wrong and make it easier to test!

[pidgezero-one]

Since the page is also used to calculate the offset, I validate it here and pass it into the template instead of defining in the template. The number of values being passed to the template is quite large, and this might not be totally necessary, but doing it this way lets me force invalid page values in the query param to default to page 1 (i.e. ?page=0, ?page=-1, ?page=aaaa all default to the first page) before using it to calculate the offset.