[Alt] Rely on the same information for topic filtering

as an alternative to https://github.com/geoadmin/mf-chsdi3/pull/963/files

This approach uses a chargeable parameter not to be published.

Filtering is only possible on:

<pre>
/rest/services/{topic}/MapServer?chargeable=true (not free)
/rest/services/{topic}/MapServer?chargeable=false (free)
</pre>