fix: Implement database serialization for gemini URL type

gemini/gemini_url.go

@@ -1,6 +1,7 @@
 package gemini
 
 import (
+	"database/sql/driver"
 	"fmt"
 	"net/url"
 	"strconv"
@@ -35,7 +36,14 @@ func (u *URL) Scan(value interface{}) error {
 
 func (u *URL) String() string {
 	return u.Full
-	//	return fmt.Sprintf("%s://%s:%d%s", u.Protocol, u.Hostname, u.Port, u.Path)
+}
+
+// Value implements the driver.Valuer interface
+func (u URL) Value() (driver.Value, error) {
+	if u.Full == "" {
+		return nil, nil
+	}
+	return u.Full, nil
 }
 
 func ParseURL(input string, descr string) (*URL, error) {