Introduce identical changes to upstream PR

This PR contains the same exact changes as my PR targeting the upstream repo[1], but consolidated into a single commit for convenience.

1: Azure#43228

Author: micah-press

sdk/openai/azure-ai-openai/src/main/java/com/azure/ai/openai/OpenAIClientBuilder.java

@@ -3,7 +3,7 @@
 // Code generated by Microsoft (R) TypeSpec Code Generator.
 package com.azure.ai.openai;
 
-import static com.azure.ai.openai.implementation.NonAzureOpenAIClientImpl.OPEN_AI_ENDPOINT;
+import static com.azure.ai.openai.implementation.NonAzureOpenAIClientImpl.OPEN_AI_ENDPOINT_PATTERN;
 
 import com.azure.ai.openai.implementation.NonAzureOpenAIClientImpl;
 import com.azure.ai.openai.implementation.OpenAIClientImpl;
@@ -333,7 +333,7 @@ private HttpPipeline createHttpPipeline() {
     private NonAzureOpenAIClientImpl buildInnerNonAzureOpenAIClient() {
         HttpPipeline localPipeline = (pipeline != null) ? pipeline : createHttpPipeline();
         NonAzureOpenAIClientImpl client
-            = new NonAzureOpenAIClientImpl(localPipeline, JacksonAdapter.createDefaultSerializerAdapter());
+            = new NonAzureOpenAIClientImpl(localPipeline, JacksonAdapter.createDefaultSerializerAdapter(), endpoint);
         return client;
     }
 
@@ -362,11 +362,11 @@ public OpenAIClient buildClient() {
     private static final ClientLogger LOGGER = new ClientLogger(OpenAIClientBuilder.class);
 
     /**
-     * OpenAI service can be used by either not setting the endpoint or by setting the endpoint to start with
-     * "https://api.openai.com/"
+     * OpenAI service can be used by either not setting the endpoint or by setting the endpoint to a
+     * URL like "https://api.openai.com/v1" or "https://eu.api.openai.com/v1".
      */
     private boolean useNonAzureOpenAIService() {
-        return endpoint == null || endpoint.startsWith(OPEN_AI_ENDPOINT);
+        return endpoint == null || OPEN_AI_ENDPOINT_PATTERN.matcher(endpoint).matches();
     }
 
     private void validateClient() {