Add support for cleaning up data from releases_json/release_assets

[bhearsum]

This was never implemented when we added these tables. Thankfully, the schemas are identical enough that the join/conditions we're using to cleanup releases works just as well here.

Even with this patch, nothing will happen immediately because I discovered that we nothing that runs the cleanup in cron since we migrated Balrog to GCP. My plan is:

• Land this
• Do some extra verification with a dry run in production
• Run the cleanup by hand in production
• Set-up a cronjob to run it on a regular basis

[gabrielBusta]

DoesDELETE FROM table_name WHERE condition work? Instead of DELETE table_name FROM table_name WHERE condition

[bhearsum]

As I understand it, when you're joining in a delete you must include the table name that you want to delete from (https://www.dofactory.com/sql/delete-join).

(I had to look this up when I was writing this, heh.)

[jcristau]

Looks like it's either DELETE tbl_name FROM tbl_name LEFT JOIN ... or DELETE FROM tbl_name USING tbl_name LEFT JOIN ..., when multiple tables are involved.
(https://dev.mysql.com/doc/refman/8.0/en/delete.html#idm45611665301776)

[Edit: link to mysql 8.0 doc instead of 5.7]

[jcristau]

Looks like it's either DELETE tbl_name FROM tbl_name LEFT JOIN ... or DELETE FROM tbl_name USING tbl_name LEFT JOIN ..., when multiple tables are involved.
(https://dev.mysql.com/doc/refman/8.0/en/delete.html#idm45611665301776)

[Edit: link to mysql 8.0 doc instead of 5.7]