refactor(types)!: remove handler and update docs (backport #17358)

[mergify]

This is an automatic backport of pull request #17358 done by Mergify.
Cherry-pick of f8f4c35 has failed:

On branch mergify/bp/release/v0.50.x/pr-17358
Your branch is up to date with 'origin/release/v0.50.x'.

You are currently cherry-picking commit f8f4c35a9.
  (fix conflicts and run "git cherry-pick --continue")
  (use "git cherry-pick --skip" to skip this patch)
  (use "git cherry-pick --abort" to cancel the cherry-pick operation)

Changes to be committed:
	modified:   docs/docs/building-modules/01-module-manager.md
	modified:   docs/docs/core/08-events.md
	modified:   server/mock/app.go
	modified:   types/handler.go

Unmerged paths:
  (use "git add <file>..." to mark resolution)
	both modified:   CHANGELOG.md

To fix up this pull request, you can check it out locally. See documentation: https://docs.github.com/en/github/collaborating-with-pull-requests/reviewing-changes-in-pull-requests/checking-out-pull-requests-locally

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