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.

This module blocks configured queries that change server state.

E.g. to make vCard storage read-only:

``` lua
readonly_stores = {
	vcard = { "vcard-temp", "vCard" };
}
```