[Feat]: Samples for implementing RPC extension

### Is your feature request related to a problem? Please describe.

Unless I'm missing something, I've been unable to find a complete extension example that implements a RPC method extension.

### Describe the solution you'd like

An example that follows best practices for implementing a custom RPC method extension and what is needed from a client and server perspective.

### Describe alternatives you've considered

_No response_

### Additional context

_No response_

### Code of Conduct

- [x] I agree to follow this project's Code of Conduct