feat(core): add shared error handling tools for web services

[petermetz]

There has to be a common and well documented way of throwing errors inside plugin implementations that the web service endpoint classes can re-use in their catch blocks.

It might also make sense to have a common utility for defining the web services themselves which would internally handle the distinction between unexpected and expected exceptions (no pun intended).

Once we have this common code in place, we can start working on the bigger refactoring of all the web services' error handling that are part of this epic.