feat: column description – backend

[BenedictHomuth]

Description

This PR includes the backend part for #4280.

For now I coined the term to be column "Description". When it should be column "Subtitle", we should change this before merging.

Changelog

• added SQL migration file
• added needed logic to backend code
• updated the go tests
• updated the postman collection

[github-actions]

The deployment to the dev cluster was successful. You can find the deployment here: https://4331.development.scrumlr.fra.ics.inovex.io
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To redeploy rerun the workflow.
DO NOT STORE IMPORTANT DATA ON THIS DEPLOYMENT

Deployed Images

• ghcr.io/inovex/scrumlr.io/scrumlr-frontend:sha-9670fc2

• ghcr.io/inovex/scrumlr.io/scrumlr-server:sha-9670fc2

[octomind-dev]

🐙 Octomind

Test Report: 13/14 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	Failed ❌	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: 9670fc2

[mateo-ivc]

lgtm