kordophone: add support for /messages

kordophone/src/api/mod.rs

@@ -1,5 +1,7 @@
 use async_trait::async_trait;
-pub use crate::model::Conversation;
+pub use crate::model::{
+    Conversation, Message, ConversationID
+};
 use crate::model::JwtToken;
 
 pub mod http_client;
@@ -17,6 +19,9 @@ pub trait APIInterface {
     // (GET) /conversations
     async fn get_conversations(&mut self) -> Result<Vec<Conversation>, Self::Error>;
 
+    // (GET) /messages
+    async fn get_messages(&mut self, conversation_id: &ConversationID) -> Result<Vec<Message>, Self::Error>;
+
     // (POST) /authenticate
     async fn authenticate(&mut self, credentials: Credentials) -> Result<JwtToken, Self::Error>;
 }