mod_http_oauth2: Return status 405 for GET to endpoints without GET handler Endpoints that only do POST have the weird side effect that a GET query to them return 404, which doesn't quite feel like the right semantics.

This module blocks configured queries that change server state.

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

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