Backport #28302 by @yp05327
Close #28287
## How to test it in local
convert Makefile L34 into:
```
cd .tmp/upstream-docs && git clean -f && git reset --hard && git fetch origin pull/28302/head:pr28302 && git switch pr28302
```
Co-authored-by: yp05327 <576951401@qq.com>
This PR is an extended implementation of #25189 and builds upon the
proposal by @hickford in #25653, utilizing some ideas proposed
internally by @wxiaoguang.
Mainly, this PR consists of a mechanism to pre-register OAuth2
applications on startup, which can be enabled or disabled by modifying
the `[oauth2].DEFAULT_APPLICATIONS` parameter in app.ini. The OAuth2
applications registered this way are being marked as "locked" and
neither be deleted nor edited over UI to prevent confusing/unexpected
behavior. Instead, they're being removed if no longer enabled in config.
The implemented mechanism can also be used to pre-register other OAuth2
applications in the future, if wanted.
Co-authored-by: hickford <mirth.hickford@gmail.com>
Co-authored-by: wxiaoguang <wxiaoguang@gmail.com>
---------
Co-authored-by: M Hickford <mirth.hickford@gmail.com>
Co-authored-by: wxiaoguang <wxiaoguang@gmail.com>
This PR cleans up the docs in a way to make them simpler to ingest by
our [docs repo](https://gitea.com/gitea/gitea-docusaurus).
1. It includes all of the sed invocations our ingestion did, removing
the need to do it at build time.
2. It replaces the shortcode variable replacement method with
`@variable@` style, simply for easier sed invocations when required.
3. It removes unused files and moves the docs up a level as cleanup.
---------
Signed-off-by: jolheiser <john.olheiser@gmail.com>
