GraphQL guide simplifications

[FroMage]

Following the GraphQL guide I noticed that we're:

• Showing some large Film and Hero DTOs using lots of “dumb” accessors, when replacing them with public fields would work just as well and make the docs shorter and easier to read.
• Showing @Name("filmId") when it's actually optional and we could use the parameter name, inducing me to falsly believe this was required.
• I'm told I need to use @Inject Context by https://quarkus.io/guides/smallrye-graphql#context when trying to add it as a query method parameter appeared to Just Work.

Perhaps we can simplify the guide around these topics?

[quarkus-bot]

/cc @jmartisk, @phillip-kruger

[phillip-kruger]

Sounds good. I'll fix a.s.a.p

[FroMage]

Thanks a lot! And also congrats on getting all those things right: they just worked when I tried them out, even though they were not documented in the guide :)