Add custom scalar support to client value formatter

[sap-ali]

In the event that a request contains fields that are objects and within those objects there are field definitions with a type other than the primitives in the ValueFormatter, such as:

class CreateEntity {
    List<DependentEntity> dependent;
}
class DependentEntity {
    MyCustomScalar value;
}
class MyCustomScalar implements CustomStringScalar {
...
}

an IllegalStateException is thrown as below:

java.lang.IllegalStateException: Could not format class MyCustomScalar: Unsupported type.
	at io.smallrye.graphql.client.impl.core.utils.ValueFormatter.format(ValueFormatter.java:48)
	at io.smallrye.graphql.client.impl.core.InputObjectFieldImpl.build(InputObjectFieldImpl.java:14)
	at io.smallrye.graphql.client.impl.core.InputObjectImpl.build(InputObjectImpl.java:14)
	at io.smallrye.graphql.client.impl.core.utils.ValueFormatter.format(ValueFormatter.java:34)
	at io.smallrye.graphql.client.impl.core.utils.ValueFormatter._processIterable(ValueFormatter.java:63)
	at io.smallrye.graphql.client.impl.core.utils.ValueFormatter.format(ValueFormatter.java:41)
	at io.smallrye.graphql.client.impl.core.InputObjectFieldImpl.build(InputObjectFieldImpl.java:14)
	at io.smallrye.graphql.client.impl.core.InputObjectImpl.build(InputObjectImpl.java:14)
	at io.smallrye.graphql.client.impl.core.utils.ValueFormatter.format(ValueFormatter.java:34)
	at io.smallrye.graphql.client.impl.core.ArgumentImpl.build(ArgumentImpl.java:12)
	at io.smallrye.graphql.client.impl.core.FieldImpl._buildArgs(FieldImpl.java:45)
	at io.smallrye.graphql.client.impl.core.FieldImpl.build(FieldImpl.java:19)
	at io.smallrye.graphql.client.impl.core.OperationImpl.lambda$buildWrapper$0(OperationImpl.java:77)
	at java.base/java.util.Arrays$ArrayList.forEach(Arrays.java:4305)
	at io.smallrye.graphql.client.impl.core.OperationImpl.buildWrapper(OperationImpl.java:77)
	at io.smallrye.graphql.client.impl.core.OperationImpl._buildFields(OperationImpl.java:68)
	at io.smallrye.graphql.client.impl.core.OperationImpl.build(OperationImpl.java:43)
	at io.smallrye.graphql.client.impl.core.DocumentImpl.build(DocumentImpl.java:11)
	at io.smallrye.graphql.client.vertx.dynamic.VertxDynamicGraphQLClient.buildRequest(VertxDynamicGraphQLClient.java:384)
	at io.smallrye.graphql.client.vertx.dynamic.VertxDynamicGraphQLClient.executeSync(VertxDynamicGraphQLClient.java:115)

However, when the field is actually a custom scalar, the formatter should be able to support the serialization. This PR fixes the issue with the formatter.

[phillip-kruger]

Can you do do a full build locally and commit again (so the formatter wont complain)

[jmartisk]

I'm not sure how exactly this is intended to be used - AFAIR we don't have any CustomScalar support in the client library, so I can't imagine how this could be put to work - but maybe I'm missing something - could you demonstrate it with a higher level test or something?

[phillip-kruger]

Maybe from another client (like JavaScript ?)

[jmartisk]

No, this is a change in our client's code. I never tried to use CustomScalars with a client, so I'm surprised this (maybe) somehow works. If it does, we should have an integration test as well as some documentation to demonstrate it

[phillip-kruger]

O, sorry, I thought this was the server side. Ignore me :)

[t1]

I think the problem is that the CustomStringScalar et.al. are not part of the client API. The dependencies of the modules should prevent this code from building, shouldn't it?

[t1]

BTW: I didn't want to say that it would not be useful to have this.