http: allow custom User-Agent for outgoing HTTP requests

internal/backend/httpuseragent_roundtripper_test.go

@@ -0,0 +1,50 @@
+package backend
+
+import (
+	"net/http"
+	"net/http/httptest"
+	"testing"
+)
+
+func TestCustomUserAgentTransport(t *testing.T) {
+	// Create a mock HTTP handler that checks the User-Agent header
+	handler := http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		userAgent := r.Header.Get("User-Agent")
+		if userAgent != "TestUserAgent" {
+			t.Errorf("Expected User-Agent: TestUserAgent, got: %s", userAgent)
+		}
+		w.WriteHeader(http.StatusOK)
+	})
+
+	// Create a test server with the mock handler
+	server := httptest.NewServer(handler)
+	defer server.Close()
+
+	// Create a custom user agent transport
+	customUserAgent := "TestUserAgent"
+	transport := &httpUserAgentRoundTripper{
+		userAgent: customUserAgent,
+		rt:        http.DefaultTransport,
+	}
+
+	// Create an HTTP client with the custom transport
+	client := &http.Client{
+		Transport: transport,
+	}
+
+	// Make a request to the test server
+	resp, err := client.Get(server.URL)
+	if err != nil {
+		t.Fatalf("Unexpected error: %v", err)
+	}
+	defer func() {
+		if err := resp.Body.Close(); err != nil {
+			t.Log("failed to close response body")
+		}
+	}()
+
+	// Check the response status code
+	if resp.StatusCode != http.StatusOK {
+		t.Errorf("Expected status code: %d, got: %d", http.StatusOK, resp.StatusCode)
+	}
+}