Enhance followed searches to include record_category

[josh-chamberlain]

Context

We currently capture the location of a followed search; however, someone could create a search for a location and filter by record category. They could reasonably expect that following a search would include only the selected categories.

Requirements

• update POST /search/follow to accept record_categories
• update GET /search/follow to return record_categories followed for a given search
  • GET /user/recent-searches works like this currently
• the front end can then include this as wireframed

Tests

I defer.

[josh-chamberlain]

Per @maxachis: Updated follows is simple enough, but this also will require adjusting the notifications architecture, which was designed to pull only on subscribed locations. This is probably a 1–2 day issue.