Function assign_model 

pub async fn assign_model(
    environment: &Environment,
    app_id: &str,
    app_secret: &str,
    access_token: &str,
    onde_app_id: &str,
    model_id: &str,
) -> Result<(), GresiqError>

Assign a catalog model to an app. Creates the record if none exists yet.

PATCH /v1/client/gresiq/apps/{onde_app_id}/model — body: { "model_id": "..." }