Fix invalid FAIL codes in REGISTER (#2269)

* nickserv.go: Update FAIL codes to match spec

* handlers.go: Fix FAIL code

* use ACCOUNT_EXISTS for errNameReserved

* bump irctest to development version

---------

Co-authored-by: Valerie Liu <79415174+ValwareIRC@users.noreply.github.com>

Author: slingamn

irc/handlers.go

@@ -2974,7 +2974,7 @@ func registerHandler(server *Server, client *Client, msg ircmsg.Message, rb *Res
 			announcePendingReg(client, rb, accountName)
 		}
 	case errAccountAlreadyRegistered, errAccountAlreadyUnregistered, errAccountMustHoldNick:
-		rb.Add(nil, server.name, "FAIL", "REGISTER", "USERNAME_EXISTS", accountName, client.t("Username is already registered or otherwise unavailable"))
+		rb.Add(nil, server.name, "FAIL", "REGISTER", "ACCOUNT_EXISTS", accountName, client.t("Username is already registered or otherwise unavailable"))
 	case errAccountBadPassphrase:
 		rb.Add(nil, server.name, "FAIL", "REGISTER", "INVALID_PASSWORD", accountName, client.t("Password was invalid"))
 	default:

irc/nickserv.go

@@ -1055,10 +1055,10 @@ func nsSaregisterHandler(service *ircService, server *Server, client *Client, co
 		var failCode string
 		if err == errAccountAlreadyRegistered || err == errAccountAlreadyVerified {
 			errMsg = client.t("Account already exists")
-			failCode = "USERNAME_EXISTS"
+			failCode = "ACCOUNT_EXISTS"
 		} else if err == errNameReserved {
 			errMsg = client.t(err.Error())
-			failCode = "USERNAME_EXISTS"
+			failCode = "ACCOUNT_EXISTS"
 		} else if err == errAccountBadPassphrase {
 			errMsg = client.t("Passphrase contains forbidden characters or is otherwise invalid")
 			failCode = "INVALID_PASSWORD"