Serialize support on types

[CKarper]

Is there a reason none of the types derive Serialize? It would be nice to build messages with these structs, but then I can't turn them into JSON using serde.

[dten]

https://docs.rs/slack_api/0.21.0/slack_api/chat/fn.post_message.html

The structs are intended for use with the api functions

[CKarper]

I was hoping to use them for building Dialogflow message objects in response to slack sourced events.

My bot routes responses both through DF, and directly using the API. What would be the lift to add the Serialization annotations to the fields? I'm new to Rust, so I can't jump in and effectively PR yet.

[dten]

the post_messsage function i linked currently handles the serialisation and for PostRequest and just deriving Serialize would not produce the same json. Extracting that serialising code to be called by itself would be an option