Build the subscriptions/listen params, nesting the filter under
params.notifications exactly as the draft spec's SubscriptionFilter
requires (boolean list-changed flags emitted only when set;
resourceSubscriptions as a string array of URIs). Separated so the param
shaping can be unit-tested without a live server.
Build the subscriptions/listen params, nesting the filter under params.notifications exactly as the draft spec's SubscriptionFilter requires (boolean list-changed flags emitted only when set; resourceSubscriptions as a string array of URIs). Separated so the param shaping can be unit-tested without a live server.