chore: oauth v2 stats refactor

[sanpj2292]

Description

The way in which stats are written is not easily readable. Through this PR, we are trying to make the stat emission in oauthv2 module a bit more developer friendly and readable

Linear Ticket

Resolves INT-2744

Security

• The code changed/added as part of this pull request won't create any security issues with how the software is being used.

[sanpj2292]

For reference

> strings.Join(strings.Fields(strings.ToLower("Refresh Token")), "_")
refresh_token

[codecov]

Codecov Report

Attention: Patch coverage is 93.54839% with 6 lines in your changes missing coverage. Please review.

Project coverage is 73.20%. Comparing base (2aae3ec) to head (d1692d2).
Report is 1 commits behind head on master.

Files with missing lines	Patch %	Lines
services/oauth/v2/oauth.go	94.64%	3 Missing ⚠️
services/oauth/v2/utils.go	50.00%	3 Missing ⚠️

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #5262   +/-   ##
=======================================
  Coverage   73.20%   73.20%           
=======================================
  Files         424      424           
  Lines       59967    59983   +16     
=======================================
+ Hits        43898    43911   +13     
- Misses      13606    13609    +3     
  Partials     2463     2463           

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