Add codex apply to apply a patch created from the Codex remote agent (#1528)

In order to to this, I created a new `chatgpt` crate where we can put
any code that interacts directly with ChatGPT as opposed to the OpenAI
API. I added a disclaimer to the README for it that it should primarily
be modified by OpenAI employees.


https://github.com/user-attachments/assets/bb978e33-d2c9-4d8e-af28-c8c25b1988e8

codex-rs/chatgpt/src/chatgpt_client.rs

@@ -0,0 +1,45 @@
+use codex_core::config::Config;
+
+use crate::chatgpt_token::get_chatgpt_token_data;
+use crate::chatgpt_token::init_chatgpt_token_from_auth;
+
+use anyhow::Context;
+use serde::de::DeserializeOwned;
+
+/// Make a GET request to the ChatGPT backend API.
+pub(crate) async fn chatgpt_get_request<T: DeserializeOwned>(
+    config: &Config,
+    path: String,
+) -> anyhow::Result<T> {
+    let chatgpt_base_url = &config.chatgpt_base_url;
+    init_chatgpt_token_from_auth(&config.codex_home).await?;
+
+    // Make direct HTTP request to ChatGPT backend API with the token
+    let client = reqwest::Client::new();
+    let url = format!("{chatgpt_base_url}{path}");
+
+    let token =
+        get_chatgpt_token_data().ok_or_else(|| anyhow::anyhow!("ChatGPT token not available"))?;
+
+    let response = client
+        .get(&url)
+        .bearer_auth(&token.access_token)
+        .header("chatgpt-account-id", &token.account_id)
+        .header("Content-Type", "application/json")
+        .header("User-Agent", "codex-cli")
+        .send()
+        .await
+        .context("Failed to send request")?;
+
+    if response.status().is_success() {
+        let result: T = response
+            .json()
+            .await
+            .context("Failed to parse JSON response")?;
+        Ok(result)
+    } else {
+        let status = response.status();
+        let body = response.text().await.unwrap_or_default();
+        anyhow::bail!("Request failed with status {}: {}", status, body)
+    }
+}