message: Make query signature check case-insensitive
diff: @@ -46,7 +46,7 @@ namespace iroha {
  auto qry = R"(
  SELECT count(public_key) = 1
  FROM account_has_signatory
  - WHERE account_id = :account_id AND public_key = :pk
  + WHERE account_id = :account_id AND public_key = lower(:pk)
  )";
  try {
  