[1.5.x] Fixed #21710 -- Documented User.get_short_name()

Thanks Keryn Knight for the report.

Backport of 0150830687 from master
[1.5.x] Fixed #21708 -- Added some headings to separate unrelated topics.

Thanks ashley at ashleymills.com for the suggestion.

Backport of 270f7e2167 from master