+/**
+ * convert an IDP realm into routing table entries.
+ *
+ * @param mem_ctx talloc context for the result
+ * @param realm IDP realm whose routes should be generated
+ * @param trust_router hostname for TRP connections to us
+ * @param trust_router_port TRP port of our trust router
+ * @param n_routes (output) the number of routes in the returned array
+ * @return Pointer to an array of pointers to routes
+ */