feat: ability to edit authorized integration in web UI (#12601)

Extends the UI introduced in #12558 to have edit capabilities.  (not in scope: "Add" for a new Authorized Integration will be the next update to this UI; `create-authorized-integration` CLI is still the only way to create a new record)

This PR includes a few refactoring steps.  The goal of these steps is to have `services/auth` be a single entrypoint for validating, inserting, or updating an authorized integration.  Some logic is moved out of `services/authz` because it is not authorization related, and some is moved out of `services/auth/method` to allow it to be reused during validation without creating a cyclical module dependency.

This PR also adds comprehensive validation to the more complex fields in the authorized integration, such as the issuer and claim rules.  This validation applies to the `forgejo admin user create-authorized-integration` CLI as well.

The visible UI is the same as #12558, but with a "Save" button, and the ability to display errors:

![Screenshot 2026-05-16 at 15-43-20 Authorized Integrations - Forgejo Beyond coding. We Forge](/attachments/ffaf60e2-3652-429b-a815-b339100f05f8)

## Checklist

The [contributor guide](https://forgejo.org/docs/next/contributor/) contains information that will be helpful to first time contributors. All work and communication must conform to Forgejo's [AI Agreement](https://codeberg.org/forgejo/governance/src/branch/main/AIAgreement.md). There also are a few [conditions for merging Pull Requests in Forgejo repositories](https://codeberg.org/forgejo/governance/src/branch/main/PullRequestsAgreement.md). You are also welcome to join the [Forgejo development chatroom](https://matrix.to/#/#forgejo-development:matrix.org).

### Tests for Go changes

- I added test coverage for Go changes...
  - [x] in their respective `*_test.go` for unit tests.
  - [ ] in the `tests/integration` directory if it involves interactions with a live Forgejo server.
- I ran...
  - [x] `make pr-go` before pushing

### Tests for JavaScript changes

- I added test coverage for JavaScript changes...
  - [ ] in `web_src/js/*.test.js` if it can be unit tested.
  - [x] in `tests/e2e/*.test.e2e.js` if it requires interactions with a live Forgejo server (see also the [developer guide for JavaScript testing](https://codeberg.org/forgejo/forgejo/src/branch/forgejo/tests/e2e/README.md#end-to-end-tests)).

### Documentation

- [ ] I created a pull request [to the documentation](https://codeberg.org/forgejo/docs) to explain to Forgejo users how to use this change.
- [x] I did not document these changes and I do not expect someone else to do it.
    - Documentation is on my TODO list and will be completed before release.

### Release notes

- [x] This change will be noticed by a Forgejo user or admin (feature, bug fix, performance, etc.). I suggest to include a release note for this change.
- [ ] This change is not visible to a Forgejo user or admin (refactor, dependency upgrade, etc.). I think there is no need to add a release note for this change.

Reviewed-on: https://codeberg.org/forgejo/forgejo/pulls/12601
Reviewed-by: Andreas Ahlenstorf <aahlenst@noreply.codeberg.org>

routers/api/actions/oidc.go

@@ -14,7 +14,7 @@ import (
 	"forgejo.org/modules/web"
 	web_types "forgejo.org/modules/web/types"
 	actions_service "forgejo.org/services/actions"
-	auth_method "forgejo.org/services/auth/method"
+	"forgejo.org/services/auth"
 	"forgejo.org/services/context"
 )
 
@@ -67,7 +67,7 @@ func init() {
 	web.RegisterResponseStatusProvider[*OIDCContext](func(req *http.Request) web_types.ResponseStatusProvider {
 		return req.Context().Value(oidcContextKey).(*OIDCContext)
 	})
-	auth_method.RegisterInternalIssuer("api/actions", internalIssuer{})
+	auth.RegisterInternalIssuer("api/actions", internalIssuer{})
 }
 
 func OIDCContexter() func(next http.Handler) http.Handler {