container, service: Support reloading containers on template file change

roles/container/meta/argument_specs.yaml

@@ -212,3 +212,21 @@ argument_specs:
         type: bool
         required: false
         default: true
+      container_reload_method:
+        description: |
+          How to reload configuration when systemctl reload is called
+          kill: Sends SIGHUP to the container
+          command: Runs the specified command inside the container
+        type: str
+        required: false
+        default: none
+        choices:
+          - kill
+          - command
+          - none
+      container_reload_command:
+        description: >-
+          Command to run inside container when systemctl reload is called.
+          Required if container_reload_method is command, ignored otherwise.
+        type: str
+        required: false