FFS-2175: Adding DB query to /health endpoint

[GeorgeCodes19]

Ticket

Relates to FFS-2175.

Changes

Context for reviewers

Acceptance testing

• No acceptance testing needed
  • This change will not affect the user experience (bugfix, dependency updates, etc.)
• Acceptance testing prior to merge
  • This change can be verified visually via screenshots attached below or by sending a link to a local development environment to the acceptance tester
  • Acceptance testing should be done by design for visual changes, product for behavior/logic changes, or both for changes that impact both.
• Acceptance testing after merge
  • This change is hard to test locally, so we'll test it in the demo environment (deployed automatically after merge.)
  • Make sure to notify the team once this PR is merged so we don't inadvertently deploy the unaccepted change to production. (e.g. :alert: Deploy block! @ffs-eng I just merged PR [#123] and will be doing acceptance testing in demo - please don't deploy until I'm finished!)

[tdooner]

Yep, that'll do it!

(Just for future record: it's generally not a good idea to test other systems in a healthcheck because if there's a database outage, then your web servers would all go down simultaneously. So, we can remove this in the future when we have enough traffic that we don't need to keep the database connection alive.)