enhance(actions): add OIDC workload identity support (#39052)

Adds OpenID Connect workload identity to Gitea Actions: jobs declaring
`id-token: write` can request short-lived tokens to authenticate to
cloud providers and other services without stored secrets. Tokens follow
GitHub's format, so clients like `@actions/core` and existing trust
policies carry over.

- Issuer at `/api/actions/oidc` with discovery and JWKS, signed with a
dedicated RS256 key
- GitHub's claims, including `workflow_ref`, `job_workflow_ref` and the
immutable `repo:owner@id/repo@id:ref:...` subject
- `id-token: write` or `write-all` grant it, default permissions and
fork pull requests never get it, owner and repository maximum
permissions can disable it
- Reusable workflows record the exact ref they were loaded from, and
dispatch rejects refs that only resolve through a same-named tag
- Generated signing keys are written atomically, and generated ES384 and
ES512 OAuth2 keys use their own curves instead of P-256
- `github.ref_type` is `branch` for pull request runs, like on GitHub

Fixes https://github.com/go-gitea/gitea/issues/26383
Fixes https://github.com/go-gitea/gitea/issues/33681
Docs: https://gitea.com/gitea/docs/pulls/526
Assisted-by: ChatGPT:gpt-5.6-sol, Claude Code:claude-opus-5-5
Co-authored-by: Lunny Xiao <xiaolunwen@gmail.com>
Co-authored-by: silverwind <me@silverwind.io>

models/actions/config.go

@@ -64,7 +64,7 @@ func (cfg *OwnerActionsConfig) GetMaxTokenPermissions() repo_model.ActionsTokenP
 		return *cfg.MaxTokenPermissions
 	}
 	// Default max is write for everything
-	return repo_model.MakeActionsTokenPermissions(perm.AccessModeWrite)
+	return repo_model.MakeWriteAllActionsTokenPermissions()
 }
 
 // ClampPermissions ensures that the given permissions don't exceed the maximum

models/actions/run_job.go

@@ -110,6 +110,8 @@ type ActionRunJob struct {
 	// ReusableWorkflowContent is the content of the reusable workflow specified by "uses:".
 	// Only set when IsReusableCaller is true.
 	ReusableWorkflowContent []byte `xorm:"LONGBLOB"`
+	// ReusableWorkflowRef is the fully qualified ref, or the commit, that "uses:" resolved to when the content was loaded.
+	ReusableWorkflowRef string `xorm:"VARCHAR(512) NOT NULL DEFAULT ''"`
 	// CallSecrets encodes the reusable workflow caller's "secrets:" section:
 	//   - ""           : no "secrets:" section (children only see auto-generated tokens).
 	//   - "inherit"    : the caller wrote "secrets: inherit".