use one-off unit struct for "type": "realtime" field

Author: janligudzinski

src/realtime/types.rs

@@ -44,6 +44,11 @@ pub enum RealtimeModel {
     Gpt4oMiniRealtimePreview20241217,
 }
 
+/// Unit struct representing the only possible value for `type` in the accept call payload.
+#[derive(Debug, Serialize, Deserialize, Clone)]
+#[serde(rename = "realtime")]
+pub struct RealtimeSessionType;
+
 #[derive(Debug, Serialize, Deserialize, Clone)]
 #[serde(rename_all = "lowercase")]
 pub enum RealtimeVoice {

src/v1/realtime_calls.rs

@@ -1,21 +1,21 @@
 use serde::{Deserialize, Serialize};
 
-use crate::realtime::types::RealtimeModel;
+use crate::realtime::types::{RealtimeModel, RealtimeSessionType};
 
 /// Used to start a realtime session based on an incoming call that you can then connect to over WSS with `RealtimeSipClient` from `openai_api_rs::realtime::sip`.
 /// Note that this is poorly documented by OpenAI with the only example data given in https://platform.openai.com/docs/guides/realtime-sip#handle-the-webhook and these may not be all the possible fields.
 #[derive(Debug, Serialize, Deserialize, Clone)]
 pub struct AcceptCallRequest {
     /// This is *always* `realtime`. Convenience constructor exposed to ensure this.
     #[serde(rename = "type")]
-    pub session_type: String,
+    pub session_type: RealtimeSessionType,
     pub instructions: String,
     pub model: RealtimeModel,
 }
 impl AcceptCallRequest {
     pub fn new(instructions: String, model: RealtimeModel) -> Self {
         Self {
-            session_type: "realtime".to_string(),
+            session_type: RealtimeSessionType,
             instructions,
             model,
         }