Try to stick with a schema. For instance "object-type:id" is a good idea, as in "user:1000". Dots or dashes are often used for multi-word fields, as in "comment:4321:reply.to" or "comment:4321:reply-to".
As of 5.0 the RestTemplate is in maintenance mode, with only minor requests for changes and bugs to be accepted going forward. Please, consider using the WebClient which offers a more modern API and supports sync, async, and streaming scenarios.