mod_http_oauth2: Do not enforce PKCE on Device and OOB flows PKCE does not appear to be used with the Device flow. I have found no mention of any interaction between those standards. Since no data is delivered via redirects in these cases, PKCE may not serve any purpose. This is mostly a problem because we reuse the authorization code to implement the Device and OOB flows.

# Introduction

This module sends a [version query][xep0092] to clients when they
connect, and logs the response, allowing statistics of client usage to
be recorded.

Note that since this is per connection, there will be a bias towards
mobile clients on bad connections.

## Example

    info    Running Running Swift version 4.0