Fixes#39189.
`IsUserBlockedBy` intentionally treats admin users as not blocked, but
`CanUnblockUser` was also using it to determine whether a blocking
relationship exists. If a previously blocked user is later promoted to
admin, the existing `user_blocking` record remains but can no longer be
removed.
This change separates those two concerns by adding `HasBlocking` for
checking the persisted blocking relationship. `CanUnblockUser` uses that
relationship check while `IsUserBlockedBy` keeps its existing admin-user
behavior.
A regression test verifies that an admin is still not considered blocked
while an existing blocking relationship can still be unblocked.
Use the new "form-fetch-action" for better user experience, and use
JSONError to show error messages.
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Co-authored-by: wxiaoguang <wxiaoguang@gmail.com>
Fixes: https://github.com/go-gitea/gitea/issues/36152
Enable the `nilnil` linter while adding `//nolint` comments to existing
violations. This will ensure no new issues enter the code base while we
can fix existing issues gradually.
Co-authored-by: Claude Opus 4.6 <noreply@anthropic.com>
