Follow-ups from https://github.com/go-gitea/gitea/pull/37038:
- Render the OpenAPI 3.0 spec in the API viewer, it is richer than the
Swagger 2.0 rendering
- Replace the back link with gitea-styled buttons to view both specs and
return to Gitea, flowing above swagger-ui on viewports where they would
overlap the title
- Key `VisibilityModes` by the string enum type, now named
`VisibilityString`, removing the `string()` casts at API call sites
- Drop the raw visibility strings from the `Service` settings struct in
favor of the typed mode fields, which also removes the org default
visibility row from the admin config page
- Fix two pre-existing issues surfaced in review: an invalid
`DEFAULT_USER_VISIBILITY` was silently accepted as public, and the org
visibility error message showed the enum zero value instead of the
submitted input
Co-authored-by: wxiaoguang <wxiaoguang@gmail.com>
Fix#33966
```
;; User must sign in to view anything.
;; It could be set to "expensive" to block anonymous users accessing some pages which consume a lot of resources,
;; for example: block anonymous AI crawlers from accessing repo code pages.
;; The "expensive" mode is experimental and subject to change.
;REQUIRE_SIGNIN_VIEW = false
```
Replace #20257 (which is stale and incomplete)
Close#20255
Major changes:
* Deprecate the "WHITELIST", use "ALLOWLIST"
* Add wildcard support for EMAIL_DOMAIN_ALLOWLIST/EMAIL_DOMAIN_BLOCKLIST
* Update example config file and document
* Improve tests
