A way to add descriptions to arguments

[peitalin]

Is your feature request related to a problem? Please describe.
Is there a way to add descriptions for arguments?

Describe the solution you'd like
A way to add descriptions to arguments, something like this in the graphql_object! macro:

    field items(
        &executor,
        #[graphql(description = "first n items")]
        first: i32,
        #[graphql(description = "last n items")]
        last: i32,
    ) -> FieldResult<Items> {
        ...
    }

Or:

#[derive(GraphQLInputObject)]
#[graphql(description = "first n items")]
type First = i32;

Which is used in the resolver as:

field item(&executor, first: First, last: Last) -> FieldResult<Item> {
    ...
}

Describe alternatives you've considered
I have looked into #[derive(GraphQLInputObject)] but that seems only for passing structs as arguments.

[peitalin]

I just realised you can do this with doc strings:

field items(
    &executor,
    /// first n items
    first: i32,
    /// last n items
    last: i32,
) -> FieldResult<Items> {
    ...
}

Or more generally:

field items(
    &executor
    #[doc = "Argument description"]
    arg_name: ArgType
    arg_name: ArgType as "Argument description"
    arg_name = default_value: ArgType as "Argument description"
) -> FieldResult<Items> {
    ...
}