Implement Int64Valuer for zeronull int types

Author: zeghong

pgtype/zeronull/int.go

@@ -32,6 +32,14 @@ func (dst *Int<%= pg_byte_size %>) ScanInt64(n int64, valid bool) error {
 	return nil
 }
 
+// Int64Value implements the [pgtype.Int64Valuer] interface.
+func (src Int<%= pg_byte_size %>) Int64Value() (pgtype.Int8, error) {
+	if src == 0 {
+		return pgtype.Int8{}, nil
+	}
+	return pgtype.Int8{Int64: int64(src), Valid: true}, nil
+}
+
 // Scan implements the database/sql Scanner interface.
 func (dst *Int<%= pg_byte_size %>) Scan(src any) error {
 	if src == nil {