Deprecate TCPSlaveBase in favour of TCPWorkerBase
Only one user known in KDE repos (kio_gopher), time to signal it (and any potential external 3rd-party) has a future-proof replacement to port to.
BTW, who is capable to write ForwardingWorkerBase in time for KF 5.101, so that the replacement API is complete? :) (sadly not up to that myself)