Example for Enum (de)serialisation

[eugenk]

There is no example of Enum serialisation/deserialisation. For instance, if I wanted to have the dog commands to be in all caps in the JSON output (and query input), what would I have to do?
https://github.com/jml/graphql-api/blob/2b64b65175a315cc8a5247aa519793f40d8b6058/tests/ExampleSchema.hs#L108-L114

Unfortunately, there is no such example. Please provide one. Also, there is no example at all for just printing an enum value (e.g. list all commands that a dog knows).