fix: no need for idna conversion in domain validator

internal/utils/app_utils.go

@@ -38,7 +38,16 @@ func SafeParseAppURL(str string) (string, error) {
 		return "", fmt.Errorf("ip addresses not allowed")
 	}
 
-	hostname, err = idna.Lookup.ToASCII(hostname)
+	i := idna.New(
+		idna.MapForLookup(),
+		idna.Transitional(false),
+		idna.BidiRule(),
+		idna.StrictDomainName(false),
+		idna.CheckHyphens(true),
+		idna.CheckJoiners(false),
+	)
+
+	hostname, err = i.ToASCII(hostname)
 
 	if err != nil {
 		return "", fmt.Errorf("failed to convert hostname to ascii: %w", err)

internal/utils/app_utils_test.go

@@ -43,6 +43,13 @@ func TestSafeParseAPPURL(t *testing.T) {
 	assert.NoError(t, err)
 	assert.Equal(t, expected, result)
 
+	// Underscores
+	appURL = "http://sub_tinyauth.app"
+	expected = "http://sub_tinyauth.app"
+	result, err = utils.SafeParseAppURL(appURL)
+	assert.NoError(t, err)
+	assert.Equal(t, expected, result)
+
 	// Lowercase
 	appURL = "HTTP://SUb.tinyAUth.aPP"
 	expected = "http://sub.tinyauth.app"
@@ -66,7 +73,7 @@ func TestSafeParseAPPURL(t *testing.T) {
 	assert.ErrorContains(t, err, "invalid url")
 
 	// Invalid punycode
-	appURL = "http://ab--cd.example.com"
+	appURL = "http://xn--h-kva.example.com"
 	_, err = utils.SafeParseAppURL(appURL)
 	assert.ErrorContains(t, err, "failed to convert hostname to ascii")