Add forwarded keys and some fixes

include/mtx/events.hpp

include/mtx/events/collections.hpp

include/mtx/events/encrypted.hpp

include/mtxclient/crypto/client.hpp

lib/crypto/client.cpp

lib/http/client.cpp

lib/structs/events.cpp

lib/structs/events/collections.cpp

lib/structs/events/encrypted.cpp

lib/structs/responses/common.cpp