* use uint8 for clarity
* unexport writeContentAsyncAndVerify
* fix typo in test function name
* remove commented interface functions
* use atomic.Int32
* cleanups in socket server activation test
* leverage stdlib's maps and slices packages
replace uses of `golang.org/x/exp/maps`
* nit: leverage `maps.Values`
* feat(general): various notifications improvements
* added API to test notification profiles
* added --http-header to webhook notification configuration
* refactored configuration to always apply defaults before persisting options in the repository
* added 'notification profile show --profile-name=X' command
* more tests
* more test coverage
* report notification code coverage