Core/DBLayer: Make database interaction after create character packet completely asynchronous. This is more performant and fixes a DoS loophole and possible data desynchronisation caused by spamming this packet.

Closes #584
Closes #2089

src/server/shared/Database/Implementation/LoginDatabase.cpp

@@ -44,4 +44,5 @@ void LoginDatabaseConnection::DoPrepareStatements()
     PREPARE_STATEMENT(LOGIN_SET_ACCOUNT_NOT_BANNED, "UPDATE account_banned SET active = 0 WHERE id = ? AND active != 0", CONNECTION_ASYNC)
     PREPARE_STATEMENT(LOGIN_DEL_REALMCHARACTERS, "DELETE FROM realmcharacters WHERE acctid = ? AND realmid = ?", CONNECTION_ASYNC)
     PREPARE_STATEMENT(LOGIN_ADD_REALMCHARACTERS, "INSERT INTO realmcharacters (numchars, acctid, realmid) VALUES (?, ?, ?)", CONNECTION_ASYNC)
+    PREPARE_STATEMENT(LOGIN_GET_SUM_REALMCHARS, "SELECT SUM(numchars) FROM realmcharacters WHERE acctid = ?", CONNECTION_ASYNC);
 }