container: Allow setting secret target

roles/container/meta/argument_specs.yaml

@@ -94,7 +94,7 @@ argument_specs:
         default: []
         elements: str
       container_secrets:
-        description: A list of secrets available to the container in /run/secrets/<secret name>
+        description: A list of secrets available to the container as file or environment variable
         type: list
         required: false
         default: []
@@ -122,6 +122,13 @@ argument_specs:
               - mount
               - env
             default: mount
+          target:
+            description: >
+              Where the secret will be available inside the container. If type is mount, this is
+              either a full file path or a filename under /run/secrets. If type is env, this is
+              the name of the environment variable. Defaults to secret name.
+            type: str
+            required: false
 
       container_env:
         description: A dict of environment variables for the container