NewMultiErr returns a MultiErr with the given errs.

UnwrapValidationError will undo .Error() boilerplate (skipping origin information, and giving .Err).

ErrorsSeparator is the expected string to use when stringifiying multiple errors to one.

ValidationError is the custom validation error which stores: - OriginType: the struct which gave the error - Err: the err to be wrapped by .Error().

MultiErr is an error interface with multiple error .Error() will retrieve the appended errs separated by ErrorsSeparator.