Cloned from https://bugzilla.redhat.com/show_bug.cgi?id=1302725
Description of problem:
Creation of a bookmark via API does not require 'public' attribute to be set, which results in 'public': null in the created entity.

Version-Release number of selected component (if applicable):

1. rpm -qa katello
   katello-2.5.0-3.nightly.el7.noarch
2. rpm -qa foreman
   foreman-1.11.0-0.develop.201601241936gitd600a50.el7.noarch
3. rpm qa foreman*
   foreman-gce-1.11.0-0.develop.201601241936gitd600a50.el7.noarch
   foreman-libvirt-1.11.0-0.develop.201601241936gitd600a50.el7.noarch
   foreman-release-1.11.0-0.develop.201601241936gitd600a50.el7.noarch
   foreman-vmware-1.11.0-0.develop.201601241936gitd600a50.el7.noarch
   foreman-selinux-1.11.0-0.develop.201601041235git6234447.el7.noarch
   foreman-ovirt-1.11.0-0.develop.201601241936gitd600a50.el7.noarch
   foreman-postgresql-1.11.0-0.develop.201601241936gitd600a50.el7.noarch
   foreman-compute-1.11.0-0.develop.201601241936gitd600a50.el7.noarch
   foreman-proxy-1.11.0-0.develop.201601211502git0a70eea.el7.noarch
   foreman-release-scl-2-1.el7.x86_64
   foreman-debug-1.11.0-0.develop.201601241936gitd600a50.el7.noarch
4. rpm qa *-katello
   pulp-katello-0.4-3.el7.noarch
   tfm-rubygem-katello-2.5.0.201601221853git276ce3d1.nightly.el7.noarch

How reproducible:
always

Steps to Reproduce:
1. send a POST request to <fqdn>/api/bookmarks specifying only a name, query and a controller attribute.

e.g.:

curl -ku admin:changeme -H Content-Type:application/json -d "{\"name\":\"foo\",\"query\":\"bar\", \"controller\":\"organizations\"}" 'https://<FQDN>/api/bookmarks'

Actual results:

{"name":"foo","controller":"organizations","query":"bar","public":null,"id":12,"owner_id":3,"owner_type":"User"}

Expected results:

public attribute should be set - so either an error should be returned forcing user to specify True/False. Or a default value should be assigned (False)