When applied on raw RPC method or method metadata parameter, customizes error message displayed
for unmatched real method.
When applied on raw RPC parameter or param metadata parameter, customizes error message displayed
when no real parameter matched annotated raw parameter. This implies that the raw parameter must have
single arity (otherwise it's not required to be matched by any real parameter).
When applied on raw RPC method or method metadata parameter, customizes error message displayed for unmatched real method.
When applied on raw RPC parameter or param metadata parameter, customizes error message displayed when no real parameter matched annotated raw parameter. This implies that the raw parameter must have
single
arity (otherwise it's not required to be matched by any real parameter).