feat(lib): add (*TraefikOidc).Ready() metadata-discovery readiness accessor

ready.go

@@ -0,0 +1,11 @@
+package traefikoidc
+
+// Ready reports whether the middleware has completed at least one successful
+// OIDC provider metadata discovery. Used by external supervisors (e.g. the
+// oidcgate /readyz endpoint) to gate traffic until the IdP discovery doc
+// has been fetched and the authorization endpoint is known.
+func (t *TraefikOidc) Ready() bool {
+	t.metadataMu.RLock()
+	defer t.metadataMu.RUnlock()
+	return t.authURL != ""
+}