[Task] Get funding address

## Description
singular address
implicitly created if doesn't exist
return address (for token transfer in), token balance

## Motivation
Describe the motivation for the feature to be developed.

## Resources
Link to any resources relevant for the task such as issues, PRs, reference implementations, or specifications.

## To-do list
Create a task-specific to-do list. Please link PRs that match the TODO list item behind the item after it has been submitted.

## Change checklist
Add an `x` to the boxes that are relevant to your changes, and delete any items that are not.

- [ ] The feature or fix is implemented in Rust and across all bindings whereas possible.
- [ ] The feature or fix has sufficient testing coverage
- [ ] All tests and examples build and run locally as expected
- [ ] Every piece of code has been document according to the documentation guidelines.
- [ ] If conceptual documentation (mdbook) and examples highlighting the feature exist, they are properly updated.
- [ ] If the feature is not currently documented, a documentation task Issue has been opened to address this.

The issue names no files, tests, or entry points, so start by locating the Rust API for funding and token transfers. Done should mean a singular address is implicitly created when absent and the API returns that address together with its token balance.

Written by the indexing model from the issue text.