Add user_data parameter to netcode_generate_connect_token

uint8_t * user_data, taken directly from netcode_generate_connect_token_private, is now a part of netcode_generate_connect_token so that creation of user data is exposed to the user. The constant NETCODE_USER_DATA_BYTES is also exposed in netcode.h for the purpose of users knowing how large the user_data array should be. To replace the previous code which was randomly generating 256 bytes for the purpose of connecting, the random user_data generation code has been copy pasted into all the code that previously used netcode_generate_connect_token without the user_data parameter. All tests are passing.

client.c

@@ -81,9 +81,12 @@ int main( int argc, char ** argv )
     netcode_random_bytes( (uint8_t*) &client_id, 8 );
     printf( "client id is %.16" PRIx64 "\n", client_id );
 
+    uint8_t user_data[NETCODE_USER_DATA_BYTES];
+    netcode_random_bytes(user_data, NETCODE_USER_DATA_BYTES);
+
     uint8_t connect_token[NETCODE_CONNECT_TOKEN_BYTES];
 
-    if ( netcode_generate_connect_token( 1, &server_address, &server_address, CONNECT_TOKEN_EXPIRY, CONNECT_TOKEN_TIMEOUT, client_id, PROTOCOL_ID, private_key, connect_token ) != NETCODE_OK )
+    if ( netcode_generate_connect_token( 1, &server_address, &server_address, CONNECT_TOKEN_EXPIRY, CONNECT_TOKEN_TIMEOUT, client_id, PROTOCOL_ID, private_key, user_data, connect_token ) != NETCODE_OK )
     {
         printf( "error: failed to generate connect token\n" );
         return 1;

client_server.c

@@ -97,7 +97,10 @@ int main( int argc, char ** argv )
     netcode_random_bytes( (uint8_t*) &client_id, 8 );
     printf( "client id is %.16" PRIx64 "\n", client_id );
 
-    if ( netcode_generate_connect_token( 1, (NETCODE_CONST char**) &server_address, (NETCODE_CONST char**) &server_address, CONNECT_TOKEN_EXPIRY, CONNECT_TOKEN_TIMEOUT, client_id, PROTOCOL_ID, private_key, connect_token ) != NETCODE_OK )
+    uint8_t user_data[NETCODE_USER_DATA_BYTES];
+    netcode_random_bytes(user_data, NETCODE_USER_DATA_BYTES);
+
+    if ( netcode_generate_connect_token( 1, (NETCODE_CONST char**) &server_address, (NETCODE_CONST char**) &server_address, CONNECT_TOKEN_EXPIRY, CONNECT_TOKEN_TIMEOUT, client_id, PROTOCOL_ID, private_key, user_data, connect_token ) != NETCODE_OK )
     {
         printf( "error: failed to generate connect token\n" );
         return 1;