refactor: Refactor endpoint and model compatibility check (#180)

* Add model check for chat stream

* Sync model checks

* Fix typo

* Fix functino

* refactor: Refactor endpoint and model compatibility check

* apply review suggestions

* minor fix

* invert return boolean flag

* fix test

request_builder_test.go

@@ -61,7 +61,7 @@ func TestClientReturnsRequestBuilderErrors(t *testing.T) {
 		t.Fatalf("Did not return error when request builder failed: %v", err)
 	}
 
-	_, err = client.CreateChatCompletionStream(ctx, ChatCompletionRequest{})
+	_, err = client.CreateChatCompletionStream(ctx, ChatCompletionRequest{Model: GPT3Dot5Turbo})
 	if !errors.Is(err, errTestRequestBuilderFailed) {
 		t.Fatalf("Did not return error when request builder failed: %v", err)
 	}