mod_http_oauth2: Stricten check of urlencoded form data Because type(formdecode("string without equals sign")) == "string", so best avoid continuing in that case, even if strings mostly behave as tables as long as you don't hit one of the __index methods.

This module blocks configured queries that change server state.

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

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