[ Bug Fix ] change json tag for ConversationMessage field in Conversation struct

[anshal21]

Why?

As per the conversation model documentation here https://developers.intercom.com/intercom-api-reference/reference#conversation-model
It does not have any field with the name conversation_message and there is no such field available in the response as well

Though as per the code comments

// A ConversationMessage is the message that started the conversation rendered for presentation

Which maps to the source field mentioned in the documentation

The Conversation Part that originated this conversation, which can be Contact, Admin, Campaign, Automated or Operator initiated.

Based on this, we should be populating the ConversationMessage struct from the source field in the response

How?

Technical details on your change

• Changed the json tag for ConversationMessage field in the Conversation struct from conversation_message to source, which fixes the issue