Accept usernames as email format

internal/utils/address.go

@@ -0,0 +1,19 @@
+package utils
+
+import (
+	"fmt"
+	"strings"
+)
+
+const TLD = ".yggmail"
+
+func ParseAddress(email string) (string, string, error) {
+	if !strings.HasSuffix(email, TLD) {
+		return "", "", fmt.Errorf("invalid TLD")
+	}
+	at := strings.LastIndex(email, "@")
+	if at == 0 {
+		return "", "", fmt.Errorf("invalid email address")
+	}
+	return email[:at], strings.TrimSuffix(email[at+1:], TLD), nil
+}