Add interceptor that catches panics
Right now a panic in any single RPC call will crash the entire server. This is not how things work elsewhere in our stack; we should catch these panics. An interceptor seems the way to do it.
This is an example: https://github.com/kazegusuri/grpc-panic-handler
Considering how small this is I think we should consider rolling our own interceptor rather than to add this the one linked above as a dependency.