Fix provider schema for goauthentik/authentik 2026.5.0

- group: parent → parents (list)
- saml/oauth2: add required invalidation_flow
- oauth2: remove redirect_uris (use allowed_redirect_uris via config)
- ldap: replace authorization_flow/search_group with bind_flow/unbind_flow
- Add versions.tf with required_providers block
- Remove service_connection from outpost (auto-discovered)

modules/authentik/versions.tf

@@ -0,0 +1,9 @@
+terraform {
+  required_version = ">= 1.10"
+  required_providers {
+    authentik = {
+      source  = "goauthentik/authentik"
+      version = ">= 2026.5.0"
+    }
+  }
+}