fix: Fix username extraction in the TLS handler

internal/dns/username.go

@@ -0,0 +1,15 @@
+package dns
+
+import "strings"
+
+// Extract the username from the domain name @domain that we're processing
+// at the moment.
+func ExtractUsername(pagesDomain, domain string) string {
+	suffixlessDomain := strings.TrimSuffix(domain, "."+pagesDomain)
+	usernameParts := strings.Split(suffixlessDomain, ".")
+	if len(usernameParts) == 1 {
+		return usernameParts[0]
+	}
+
+	return strings.Join(usernameParts, ".")
+}

internal/dns/username_test.go

@@ -0,0 +1,23 @@
+package dns
+
+import "testing"
+
+func TestExtractUsernameSimple(t *testing.T) {
+	username := ExtractUsername(
+		"pages.local",
+		"papatutuwawa.pages.local",
+	)
+	if username != "papatutuwawa" {
+		t.Fatalf("Unexpected username: '%s'", username)
+	}
+}
+
+func TestExtractUsernameDot(t *testing.T) {
+	username := ExtractUsername(
+		"pages.local",
+		"polynom.me.pages.local",
+	)
+	if username != "polynom.me" {
+		t.Fatalf("Unexpected username: '%s'", username)
+	}
+}