API route trailing slash validation accidentally removed

[sarayourfriend]

Description

WordPress/openverse-api#806 added the validateopenapischema management command primarily to confirm that trailing slashes would no longer accidentally be left off of routes. We unintentionally removed the management command in #1876, probably because it used the old schema generator and we missed that it was doing more than just checking that the schema was valid.

Fix

Add a new management command called checktrailingslashes and add it to CI in the Django checks section.

Additional context

Pinging @dhruvkb to make sure that I'm not missing something that still covers the trailing slash issue.

[ArtOf-Coding]

Hey @sarayourfriend, I would like to work on this issue. Can you please assign this issue to me..