The desire for `PATCH` was to make it simple to update single values in AppDefinitions without having to supply the full config again.

    # Implies all values besides `instances` should be set to default values,
    # should likely return an error since it's missing required attributes.
    PUT /v2/apps/app_3 "{'instances': 3}"

    # Implies only the `instances` value should be updated
    PATCH /v2/apps/app3 "{'instances': 3}"