title: Request specific challenge with ACME client library
body: <p>How to request specific challenge (<code>TLSSNI01</code>) from the server?</p>
  
  <p>Currently only <code>DNS01</code>, <code>HTTP01</code>, <code>TLSALPN01</code> are returned and I don't see any place where it could be specified by reading <a href="https://acme-python.readthedocs.io/en/latest/index.html" rel="nofollow noreferrer">https://acme-python.readthedocs.io/en/latest/index.html</a></p>