store: add the names codes_only setting

scripts/store-service/store_service.ini.example

@@ -101,6 +101,8 @@ private_key = replace-me
 ;reveal_margin_seconds = 900
 ; how many times one order may move to another name
 ;max_order_moves = 3
+; on: only prepaid codes register names, and every paid name order answers 403 codes_only
+;codes_only = off
 ;
 ; community names, with [names] only: one line per name, `<label> = <what it is for>`, the label in
 ; lower case and listed once, the text 1 to 200 characters without a full stop at the end, which