The SCIM endpoints are served by the elimity-com/scim library mounted as
a single prefix handler on the root ServeMux, so they are never
registered as individual gorilla/mux routes.
Since the routes can't be discovered, supply them to the validator
instead: add scim.RegisterValidationRoutes, a FeatureRouteFunc that
registers stub routes for the SCIM endpoints (handlers are never
invoked, only their path templates and methods are inspected). Wire it
into the three Validate call sites (production serve, test helper,
svctest).
Juan Fernandez
ed14c5385c