feature: use CustomObjectMapper to serialize subscription data

[clayembry]

Describe the Feature Request

A CustomObjectMapper can be supplied for serializing GraphQL responses. But that object mapper is not used to serialize subscription data. The objectMapper used to serialize subscription data is instantiated in the companion object for the WebsocketGraphQLWSProtocolHandler class.

This is causing our subscriptions to fail sending data because the objects we are trying to send contain OffsetDateTime fields that cause the ObjectMapper to throw exceptions because the JavaTimeModule is not registered with the subscription ObjectMapper.

Describe Preferred Solution

Please consider injecting the CustomObjectMapper into the WebsocketGraphQLWSProtocolHandler class to use for serializing subscription data.

[coleturner]

Hey @clayembry 👋

Our team met to discuss this issue and we came to the conclusion that we would prefer to internalize the mapping of objects used across the DGS framework, so we will instead add JavaTimeModule. Thanks for your patience as we hope to release this in the next week or two.

[clayembry]

@coleturner - your fix did not fix the problem we are facing. Because neither WebsocketGraphQLWSProtocolHandler or WebsocketGraphQLTransportWSProtocolHandler inject the dgsObjectMapper.

Both of those classes that we are having issues with just instantiate their own plain ObjectMapper in the companion object using val objectMapper = jacksonObjectMapper().

• https://github.com/Netflix/dgs-framework/blob/master/graphql-dgs-subscriptions-websockets/src/main/kotlin/com/netflix/graphql/dgs/subscriptions/websockets/WebsocketGraphQLTransportWSProtocolHandler.kt#L226
• https://github.com/Netflix/dgs-framework/blob/master/graphql-dgs-subscriptions-websockets/src/main/kotlin/com/netflix/graphql/dgs/subscriptions/websockets/WebsocketGraphQLWSProtocolHandler.kt#L151

Please fix so that those two classes inject the dgsObjectMapper and use it instead.