Add support for `delivery_estimate` besides the reach estimates

[flovv]

I am using the command reachestimate - v2.9:

> esti <- fbad_reachestimate(targeting_spec = targeting_spec, currency = "EUR", optimize_for = "REACH" )
> esti
$users
[1] 12000000

previously the call returned much more information. Also return data looks different in this post: https://stackoverflow.com/questions/24782045/can-i-get-a-facebook-reach-estimate-from-the-api-without-paying-for-an-ad

[daroczig]

Yeah, the API is changing from version to version -- at Facebook, it's not at the R package level: https://developers.facebook.com/docs/apps/changelog#v2_9_targeting

See the delivery_estimate API endpoint. I'm modifying this ticket to add support to this new API endpoint

[flovv]

Thanks, right it is more an enhancement. I tried to run this GET command "https://graph.facebook.com/v2.9/<account-ID>/delivery_estimate?currency=US&access_token=<token>&targeting_spec={\"currency\":[\"USD\"],\"targeting_spec\":[\"{\\\"age_min\\\":20,\\\"age_max\\\":49,\\\"genders\\\":[2],\\\"geo_locations\\\":{\\\"countries\\\":[\\\"DE\\\"]}}\"],\"optimize_for\":[\"REACH\"]}"

but I get the following reponse:

$error$error_user_msg [1] "Your audience targeting is incomplete. Select at least one location, or choose a Custom Audience."

Any ideas?