Detect N+1 errors in development

[JPrevost]

Why are these changes being introduced:

• This app has a history of poor performance in production that we have been able to slowly adjust by investigating N+1 queries
• The bullet gem gives us a more structured way of detecting, logging, and addressing these types of issues during development so we can avoid pushing new problems into production

Relevant ticket(s):

• https://mitlibraries.atlassian.net/browse/ETD-569
• https://mitlibraries.atlassian.net/browse/ETD-570
• https://mitlibraries.atlassian.net/browse/ETD-609
• https://mitlibraries.atlassian.net/browse/ETD-608

How does this address that need:

• Adds Bullet gem and associated configuration
• Using application in development and test envs, used the information provided to address N+1 queries and removed a few over eager loads.

Document any side effects to this change:

• Running Bullet as part of our test suite would be ideal, but administrate is a bit complicated to fix the reported issues. We could probably ignore all of the administrate errors, but it was not yet clear if that was a good path so leaving it disabled in test is the current plan.
• There are some over eager loads that track back to ActiveStorage. From my reading of the documentation, we are doing the calls properly so it wasn't clear yet how to proceed.

Developer

• All new ENV is documented in README
• All new ENV has been added to Heroku Pipeline, Staging and Prod
• ANDI or Wave has been run in accordance to
  our guide and
  all issues introduced by these changes have been resolved or opened as new
  issues (link to those issues in the Pull Request details above)
• Stakeholder approval has been confirmed (or is not needed)

Code Reviewer

• The commit message is clear and follows our guidelines
  (not just this pull request message)
• There are appropriate tests covering any new functionality
• The documentation has been updated or is unnecessary
• The changes have been verified
• New dependencies are appropriate or there were no changes

Requires database migrations?

NO

Includes new or updated dependencies?

YES

[coveralls]

Coverage: 98.304% (+0.0008%) from 98.303% when pulling 1f2e74a on bullet into d33b44a on main.

[jazairi]

I haven't tested this with prod data to see how it affects real-world performance, but the changes here make sense to me. I agree with the decision not to enable bullet in test for now. Glad you stumbled upon this gem -- seems like it'll be useful!