Allow OpenAI API URL to be configured via assistant.openai_api_url (#7552)

Partially fixes #4321, since Azure OpenAI API can be converted to OpenAI
API.

Release Notes:

- Added `assistant.openai_api_url` setting to allow OpenAI API URL to be
configured.

---------

Co-authored-by: Marshall Bowers <elliott.codes@gmail.com>

crates/ai/src/providers/open_ai/completion.rs

@@ -103,6 +103,7 @@ pub struct OpenAiResponseStreamEvent {
 }
 
 pub async fn stream_completion(
+    api_url: String,
     credential: ProviderCredential,
     executor: BackgroundExecutor,
     request: Box<dyn CompletionRequest>,
@@ -117,7 +118,7 @@ pub async fn stream_completion(
     let (tx, rx) = futures::channel::mpsc::unbounded::<Result<OpenAiResponseStreamEvent>>();
 
     let json_data = request.data()?;
-    let mut response = Request::post(format!("{OPEN_AI_API_URL}/chat/completions"))
+    let mut response = Request::post(format!("{api_url}/chat/completions"))
         .header("Content-Type", "application/json")
         .header("Authorization", format!("Bearer {}", api_key))
         .body(json_data)?
@@ -195,18 +196,20 @@ pub async fn stream_completion(
 
 #[derive(Clone)]
 pub struct OpenAiCompletionProvider {
+    api_url: String,
     model: OpenAiLanguageModel,
     credential: Arc<RwLock<ProviderCredential>>,
     executor: BackgroundExecutor,
 }
 
 impl OpenAiCompletionProvider {
-    pub async fn new(model_name: String, executor: BackgroundExecutor) -> Self {
+    pub async fn new(api_url: String, model_name: String, executor: BackgroundExecutor) -> Self {
         let model = executor
             .spawn(async move { OpenAiLanguageModel::load(&model_name) })
             .await;
         let credential = Arc::new(RwLock::new(ProviderCredential::NoCredentials));
         Self {
+            api_url,
             model,
             credential,
             executor,
@@ -303,7 +306,8 @@ impl CompletionProvider for OpenAiCompletionProvider {
         // which is currently model based, due to the language model.
         // At some point in the future we should rectify this.
         let credential = self.credential.read().clone();
-        let request = stream_completion(credential, self.executor.clone(), prompt);
+        let api_url = self.api_url.clone();
+        let request = stream_completion(api_url, credential, self.executor.clone(), prompt);
         async move {
             let response = request.await?;
             let stream = response

crates/ai/src/providers/open_ai/embedding.rs

@@ -35,6 +35,7 @@ lazy_static! {
 
 #[derive(Clone)]
 pub struct OpenAiEmbeddingProvider {
+    api_url: String,
     model: OpenAiLanguageModel,
     credential: Arc<RwLock<ProviderCredential>>,
     pub client: Arc<dyn HttpClient>,
@@ -69,7 +70,11 @@ struct OpenAiEmbeddingUsage {
 }
 
 impl OpenAiEmbeddingProvider {
-    pub async fn new(client: Arc<dyn HttpClient>, executor: BackgroundExecutor) -> Self {
+    pub async fn new(
+        api_url: String,
+        client: Arc<dyn HttpClient>,
+        executor: BackgroundExecutor,
+    ) -> Self {
         let (rate_limit_count_tx, rate_limit_count_rx) = watch::channel_with(None);
         let rate_limit_count_tx = Arc::new(Mutex::new(rate_limit_count_tx));
 
@@ -80,6 +85,7 @@ impl OpenAiEmbeddingProvider {
         let credential = Arc::new(RwLock::new(ProviderCredential::NoCredentials));
 
         OpenAiEmbeddingProvider {
+            api_url,
             model,
             credential,
             client,
@@ -130,11 +136,12 @@ impl OpenAiEmbeddingProvider {
     }
     async fn send_request(
         &self,
+        api_url: &str,
         api_key: &str,
         spans: Vec<&str>,
         request_timeout: u64,
     ) -> Result<Response<AsyncBody>> {
-        let request = Request::post(format!("{OPEN_AI_API_URL}/embeddings"))
+        let request = Request::post(format!("{api_url}/embeddings"))
             .redirect_policy(isahc::config::RedirectPolicy::Follow)
             .timeout(Duration::from_secs(request_timeout))
             .header("Content-Type", "application/json")
@@ -246,6 +253,7 @@ impl EmbeddingProvider for OpenAiEmbeddingProvider {
         const BACKOFF_SECONDS: [usize; 4] = [3, 5, 15, 45];
         const MAX_RETRIES: usize = 4;
 
+        let api_url = self.api_url.as_str();
         let api_key = self.get_api_key()?;
 
         let mut request_number = 0;
@@ -255,6 +263,7 @@ impl EmbeddingProvider for OpenAiEmbeddingProvider {
         while request_number < MAX_RETRIES {
             response = self
                 .send_request(
+                    &api_url,
                     &api_key,
                     spans.iter().map(|x| &**x).collect(),
                     request_timeout,