Fix a few clang-tidy warnings

.clang-tidy

CMakeLists.txt

include/mtx/responses/common.hpp

include/mtxclient/crypto/client.hpp

include/mtxclient/crypto/utils.hpp

include/mtxclient/http/client.hpp

lib/crypto/client.cpp

lib/crypto/encoding.cpp

lib/crypto/utils.cpp

lib/http/client.cpp

lib/structs/errors.cpp

lib/structs/responses/common.cpp

lib/structs/responses/version.cpp

lib/utils.cpp