move request_builder into internal pkg (#304) (#329)

* move request_builder into internal pkg (#304)

* add some test for internal.RequestBuilder

* add a test for openai.GetEngine

models.go

@@ -40,7 +40,7 @@ type ModelsList struct {
 // ListModels Lists the currently available models,
 // and provides basic information about each model such as the model id and parent.
 func (c *Client) ListModels(ctx context.Context) (models ModelsList, err error) {
-	req, err := c.requestBuilder.build(ctx, http.MethodGet, c.fullURL("/models"), nil)
+	req, err := c.requestBuilder.Build(ctx, http.MethodGet, c.fullURL("/models"), nil)
 	if err != nil {
 		return
 	}