Add :height param to balance endpoint and use in test

[tbro]

Adds :height param to balance endpoint. Adds client method, and use it in tests.

[tbro]

Currently getting error:

ServerError { status: StatusCode(400), message: "\0\0\u{1}\0\u{3}\0\0\0\0\0\0\0\u{1}\0\0\0\u{2}\0\0\0\u{4}\0\0\0" }