[Bug Fix] Fix for undefined MySQL library behavior. (#2834)

* MYSQL objects cannot be copied in a well defined way, this removes the copy and replaces it with another connection

* Change to share underlying pointers.

* Push up mutex changes

* Post rebase

* Formatting

---------

Co-authored-by: KimLS <KimLS@peqtgc.com>
Co-authored-by: Akkadius <akkadius1@gmail.com>

world/cli/database_concurrency.cpp

@@ -0,0 +1,73 @@
+#include <thread>
+#include "../../common/repositories/zone_repository.h"
+#include "../../common/eqemu_config.h"
+#include <signal.h>
+
+Database db;
+Database db2;
+
+volatile sig_atomic_t stop;
+void inthand(int signum) {
+	stop = 1;
+}
+
+[[noreturn]] void DatabaseTest()
+{
+	while (true) {
+		LogInfo("DatabaseTest Query");
+		db.QueryDatabase("SELECT 1");
+	}
+}
+
+[[noreturn]] void DatabaseTestSecondConnection()
+{
+	while (true) {
+		LogInfo("DatabaseTest Query");
+		db2.QueryDatabase("SELECT 1");
+	}
+}
+
+
+void WorldserverCLI::TestDatabaseConcurrency(int argc, char **argv, argh::parser &cmd, std::string &description)
+{
+	description = "Test command to test database concurrency";
+
+	if (cmd[{"-h", "--help"}]) {
+		return;
+	}
+
+	signal(SIGINT, inthand);
+
+	LogInfo("Database test");
+
+	auto mutex = new Mutex;
+
+	auto c = EQEmuConfig::get();
+	LogInfo("Connecting to MySQL");
+	if (!db.Connect(
+		c->DatabaseHost.c_str(),
+		c->DatabaseUsername.c_str(),
+		c->DatabasePassword.c_str(),
+		c->DatabaseDB.c_str(),
+		c->DatabasePort
+	)) {
+		LogError("Cannot continue without a database connection");
+		return;
+	}
+
+	db.SetMutex(mutex);
+
+	db2.SetMySQL(db);
+
+	db2.SetMutex(mutex);
+
+	std::thread(DatabaseTest).detach();
+	std::thread(DatabaseTest).detach();
+	std::thread(DatabaseTestSecondConnection).detach();
+
+	while (!stop) {
+
+	}
+
+	safe_delete(mutex);
+}