Add #[graphql(optional)] for fields (provde less boilerplate and more correctness)

[xoac]

Description of the feature

I found that in GQL I use Optional<_> fields that are actually required, because how GQL interact in Apollo Federation (for example when error is returned for some subgraph the supergraph can still return partial data if field is optional). Adding #[graphql(optioanl)] make Rust code easier to write and at the same time make GQL as expected.

Code example (if possible)

#[derive(Debug, SimpleObject)]
#[graphql(shareable)]
// maybe #[graphql(all_fileds_optional)] that can be useful for structures used in Union? 
struct Object {
  #[graphql(optional)] // this field should never be null in our service but can be in others
  name: String,
  /// this field is sometime null
  opt_filed: Option<String>,
}

[Miaxos]

Sorry I am not sure to understand the feature, why an Option<String> would not work here?

[xoac]

@Miaxos of course it will work - but you need to do a lot of Some(_) and also you can accidentally set value to None. With above you can have rust type checking system on your side. This would be only for fields that can't be null but in GQL schema are marked as nullable.

If you want to know why mark required fields as nullable read this: https://www.apollographql.com/docs/technotes/TN0023-nullability/

EDIT: updated example code to make sure that it's intentional and feature request is just syntax sugar.