`print_schema` should be deterministic

In our project, we commit a graphql schema to our repo. This is useful for running demos, tests and mocking data.

However, now we also want to be able to ensure that the schema is kept up-to-date with a CI check. Unfortunately, printing the schema twice, seems to not be guaranteed to print values in the same order (especially keys in object types, and field arguments). This makes consistency checks significantly harder.

It'd be great if there was a guarantee of determinism. Running the printer repeatedly, against a given schema always outputs the same file.

Comienza localizando el punto de entrada print_schema y cualquier prueba que cubra la salida del esquema. Comprueba cómo se ordenan los campos de los objetos y los argumentos de los campos, y verifica después que imprimir el mismo esquema repetidamente produzca una salida idéntica.

Escrito por el modelo de indexación a partir del texto del issue.