Derive Macro GraphQLFields 

#[derive(GraphQLFields)]
{
    // Attributes available to this derive:
    #[graphql]
}

Derive GraphQLFields for a struct.

Each field becomes a GraphQL selection entry:

• Plain fields → camelCaseName
• #[graphql(nested)] fields → camelCaseName { <InnerType::selection()> }

Struct-level attributes

• #[graphql(full_type = Path)] — enables compile-time validation against the specified generated type. Without this, FullType = Self and no validation is performed (used by codegen for full types).