add: UDP socket tests

test/udp_client_test.hpp

+#include "net/udp_client.hpp"
+
+#include <sys/socket.h>
+#include <sys/types.h>
+#include <netinet/in.h>
+
+namespace rmrf::net {
+
+    bool udp_test_successful = false;
+    const char* udp_test_string = "TEST UDP PACKET";
+
+    void udp_test_cb(const udp_packet<pkg_size>& data, socketaddr& source) {
+        if (strcmp(data.raw, udp_test_string) != 0)
+        udp_test_successful = true;
+    }
+
+    void run_udp_test() {
+        udp_client sender{get_first_general_socketaddr("localhost", 9862)};
+        const socketaddr destination_address = get_first_general_socketaddr("localhost", 9863);
+        udp_client receiver{destination_address, udp_test_cb};
+        udp_packet<1024> data;
+        strncpy(data.raw, udp_test_string, sizeof(udp_test_string) + 1);
+        sender.send_packet(destination, data);
+    }
+
+}