ci: review release CI triggers and Git branch model

[hwakabh]

AsIs

Currently we have release CI, where automatically generating release notes via GitHub API, with merging any PR into main.
But this makes our release note having only 1 PR line, since release.yml is basically PR-based with its label.
(whereas another solution, release-please is commit-based with conventional commits, and it would append lines to a single file, CHANGELOG.md)

ToBe

• Review release strategies regarding to git branch models
• Updated release CI if needed

(Optional) Acceptance

N/A

[hwakabh]

Reviewing back our current pipeline implementation, it turns out that we could not realize both Deploy pipelines(Backend/Frontend CIs) and Release pipeline as expected with a single production branch model.
This is because, feature of automatically generating release & its note is separated from repository code bases, where this does not require any PRs to update version, while Deploy pipeline should be triggered with merge event into default branch main.
So, these make our release note published with only a single record of merged topic branch.

For fixing this, we have to prepare at least 2 branches for productions, and make our pipelines with:

• merging topic branches into first production branch triggers Deploy pipeline
• merging first production branch into second one triggers Release pipeline

As there is a lot of branch models below, but we would adopt customized git-flow with forking releases branch from main.

• git-flow
• GitHub flow
• gitworkflow
• GitLab Flow
• Trunk-based development (Stable trunk pattern)
• mainline model

The detailed git branch strategies have been noted in Wiki, and now we can fix this issue with using releases branch with following event triggers, so will close this issue for now.

• Topic branches
  • Forked from main and are freely created/pushed by developers
  • When we merge topic branches into main, Deploy pipelines (Backend/Frontend CIs) will be triggered to push container image and updated GitHub pages
• main branch (protected)
  • Deployable code basis, and basically is expected to merge into releases for release event
  • When we merge main branch into releases, Release pipeline will be triggered to populate tags/releases/changelogs
• releases branches (protected)
  • Deployed code basis, and is associated to git tags with calendar versioning