Add support for a separate chatgpt auth endpoint (#1712)

Adds a `CodexAuth` type that encapsulates information about available
auth modes and logic for refreshing the token.
Changes `Responses` API to send requests to different endpoints based on
the auth type.
Updates login_with_chatgpt to support API-less mode and skip the key
exchange.

codex-rs/core/tests/stream_no_completed.rs

@@ -10,6 +10,7 @@ use codex_core::exec::CODEX_SANDBOX_NETWORK_DISABLED_ENV_VAR;
 use codex_core::protocol::EventMsg;
 use codex_core::protocol::InputItem;
 use codex_core::protocol::Op;
+use codex_login::CodexAuth;
 use core_test_support::load_default_config_for_test;
 use core_test_support::load_sse_fixture;
 use core_test_support::load_sse_fixture_with_id;
@@ -75,7 +76,7 @@ async fn retries_on_early_close() {
 
     let model_provider = ModelProviderInfo {
         name: "openai".into(),
-        base_url: format!("{}/v1", server.uri()),
+        base_url: Some(format!("{}/v1", server.uri())),
         // Environment variable that should exist in the test environment.
         // ModelClient will return an error if the environment variable for the
         // provider is not set.
@@ -89,13 +90,20 @@ async fn retries_on_early_close() {
         request_max_retries: Some(0),
         stream_max_retries: Some(1),
         stream_idle_timeout_ms: Some(2000),
+        requires_auth: false,
     };
 
     let ctrl_c = std::sync::Arc::new(tokio::sync::Notify::new());
     let codex_home = TempDir::new().unwrap();
     let mut config = load_default_config_for_test(&codex_home);
     config.model_provider = model_provider;
-    let CodexSpawnOk { codex, .. } = Codex::spawn(config, ctrl_c).await.unwrap();
+    let CodexSpawnOk { codex, .. } = Codex::spawn(
+        config,
+        Some(CodexAuth::from_api_key("Test API Key".to_string())),
+        ctrl_c,
+    )
+    .await
+    .unwrap();
 
     codex
         .submit(Op::UserInput {