Add driver collector

[chicobentojr]

✨ Enhancements

• Add collector to capture sql client metrics to publish using prometheus

[codecov]

Codecov Report

Merging #3 into master will decrease coverage by 2.89%.
The diff coverage is 39%.

@@            Coverage Diff            @@
##           master       #3     +/-   ##
=========================================
- Coverage   47.79%   44.89%   -2.9%     
=========================================
  Files           6        7      +1     
  Lines         860     1283    +423     
=========================================
+ Hits          411      576    +165     
- Misses        423      670    +247     
- Partials       26       37     +11

Impacted Files	Coverage Δ
promsql/driver_collector.go	39% <39%> (ø)
promfasthttp/instrument_server.go	35.16% <0%> (-0.43%)	⬇️
promhermes/instrument_server.go	36.06% <0%> (+0.4%)	⬆️

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[jamillosantos]

Please, consider adding a full example (:star2: with docker-compose) to show how to use it.

Also, would be nice to write some documentation.

[jamillosantos]

After creating this extension, I think now you are able to better understand (and I too) where we want to go with these metrics. That said...

What are we measuring with TransactionFailedCounter? And what do we want/need to measure while dealing with transactions?

[felipemfp]

LGTM 🎉👍