1. A system that routes a message between a first service and a second service on behalf of an entity in a message routing service, the system comprising: a router including at least one processor and memory coupled to the processor, the memory loaded with instructions that implement a message routing service and cause the processor to: (a) receive an authentication request for the entity at the message routing service; (b) generate at the message routing service an identifier for the authentication request, the identifier indicating authentication of the entity to the message routing service; (c) send at least one provisioning message to at least one of the first service and the second service using the message routing service, the at least one provisioning message including the identifier for provisioning the entity with the at least one of the first service and the second service; and (d) subsequent to the receiving, generating and sending: receive a message at the message routing service from the first service, the message including the identifier, the message further being directed to the second service; authenticate the message at the message routing service using the identifier; determine, upon authenticating, at the message routing service a route and a transformation comprised of one or more of no modification of the message, a modification of the message, and a translation of the message; and route an output message to the second service according to the route and the transformation of the message to form the output message from the first service, the output message including the identifier.