title: How can I use the "plain" PKCE code challenge method with AppAuth?
body: <p>By default, <a href="http://github.com/openid/AppAuth-iOS" rel="nofollow noreferrer">AppAuth</a> sends a <code>S256</code> <a href="https://www.rfc-editor.org/rfc/rfc7636" rel="nofollow noreferrer">PKCE</a> code challenge on auth requests. If I need to interoperate with a server that only supports the <code>plain</code> code challenge method, how can I configure my authorization request?</p>