feat: Prometheus metrics

[BenedictHomuth]

Description

Instrumented our application. For now, it offers a counter and histogram for all general routes of our API.

When there is a need for more, I will implement it. Just leave a comment below.

Changelog

• Established a custom metrics service.
• Exposed the /metrics endpoint, which is commonly used with Prometheus.
• Implemented a counter and histogram
• Added Grafana and Prometheus to the docker-compose dev file (for now)
• Added server/src/tmp to gitignore, since I currently use air, which otherwise would create an unwanted folder there.

Checklist

• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• The light- and dark-theme are both supported and tested
• The design was implemented and is responsive for all devices and screen sizes
• The application was tested in the most commonly used browsers (e.g. Chrome, Firefox, Safari)

(Optional) Visual Changes

[octomind-dev]

🐙 Octomind

Test Report: 0/14 successful.

description	status	details
About Section Visibility Test	Failed ❌	click
change avatar	Failed ❌	click
check Privacy Policy	Failed ❌	click
check terms & conditions	Failed ❌	click
close cookie banner - front page	Failed ❌	click
close cookie banner - sign-in	Failed ❌	click
create and delete board columns	Failed ❌	click
create_and_delete_notes_and_actions_v2	Failed ❌	click
create lean coffee board	Failed ❌	click
edit_notes_and_actions_v5	Failed ❌	click
get started	Failed ❌	click
share_session	Failed ❌	click
sign-in	Failed ❌	click
test all ways to open the setup flow	Failed ❌	click

commit sha: 68a34d8

[github-actions]

The deployment to the dev cluster was successful. You can find the deployment here: https://4138.development.scrumlr.fra.ics.inovex.io
This deployment is only for testing purposes and will be deleted after 1 week.
To redeploy rerun the workflow.
DO NOT STORE IMPORTANT DATA ON THIS DEPLOYMENT

Deployed Images

• ghcr.io/inovex/scrumlr.io/scrumlr-frontend:sha-ba0a2c7

• ghcr.io/inovex/scrumlr.io/scrumlr-server:sha-ba0a2c7

[octomind-dev]

🐙 Octomind

Test Report: 14/14 successful.

description	status	details
About Section Visibility Test	Passed ✅	click
change avatar	Passed ✅	click
check Privacy Policy	Passed ✅	click
check terms & conditions	Passed ✅	click
close cookie banner - front page	Passed ✅	click
close cookie banner - sign-in	Passed ✅	click
create and delete board columns	Passed ✅	click
create_and_delete_notes_and_actions_v2	Passed ✅	click
create lean coffee board	Passed ✅	click
edit_notes_and_actions_v5	Passed ✅	click
get started	Passed ✅	click
share_session	Passed ✅	click
sign-in	Passed ✅	click
test all ways to open the setup flow	Passed ✅	click

commit sha: ba0a2c7