Fix some compiler warnings in public headers #891

Job	Run time
Formatting Check	1m 59s
Build with the C++20 standard	5m 36s
Build CPP Client on macOS	2m 26s
Run unit tests	17m 20s
Build the Wireshark dissector (ubuntu-20.04)	51s
Build CPP Client on macOS with static dependencies	4m 18s
Build CPP Client on Windows x64	32m 0s
Build RPM x86_64	10m 57s
Build CPP Client on Windows x86	30m 52s
Build Deb x86_64	10m 45s
Build Alpine x86_64	10m 51s
Check Completion	0s
	2h 7m 55s

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