Reduce db queries coming from health endpoint

[scott-codecov]

Purpose/Motivation

Our number 1 query by volume is our own health check endpoint

What does this PR do?

• Cache the result of the version query for the lifetime of the process.
• Perform a check on the db connection state so that the health endpoint returns 500 when the db is down.

[codecov-staging]

Codecov Report

All modified and coverable lines are covered by tests ✅

📢 Thoughts on this report? Let us know!

[codecov-public-qa]

Codecov Report

Merging #311 (cf95d9d) into main (67398dc) will increase coverage by 0.00%.
The diff coverage is 100.00%.

@@           Coverage Diff           @@
##             main     #311   +/-   ##
=======================================
  Coverage   95.95%   95.95%           
=======================================
  Files         611      611           
  Lines       15722    15729    +7     
=======================================
+ Hits        15086    15093    +7     
  Misses        636      636           

Flag	Coverage Δ
unit	95.95% <100.00%> (+<0.01%)	⬆️
unit-latest-uploader	95.95% <100.00%> (+<0.01%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

Files	Coverage Δ
codecov/views.py	100.00% <100.00%> (ø)

[codecov-qa]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (67398dc) 95.95% compared to head (cf95d9d) 95.95%.

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #311   +/-   ##
=======================================
  Coverage   95.95%   95.95%           
=======================================
  Files         611      611           
  Lines       15722    15729    +7     
=======================================
+ Hits        15086    15093    +7     
  Misses        636      636           

Flag	Coverage Δ
unit	95.95% <100.00%> (+<0.01%)	⬆️
unit-latest-uploader	95.95% <100.00%> (+<0.01%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

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