Vendor middleware_automation.keycloak collection

Needed for keycloak_authentication_v2, to manage Keycloak
authentication flows (e.g. the CCCHH browser flow) as YAML.
Chosen over community.general's own copy of the module (deprecated in
favor of this collection, and limited to 4 sub-flow levels there vs.
10 here).

requirements.yml

@@ -11,3 +11,7 @@ collections:
   - source: https://github.com/ansible-collections/community.docker
     type: git
     version: "5.0.5"
+  # middleware_automation.keycloak
+  - source: https://github.com/ansible-middleware/keycloak
+    type: git
+    version: "3.0.11"