Foreman HasManyCommon concern uses 'id' as a value of last resort for the name of an attribute. But Rails expects this value to a return a string. This causes a problem for Katello. Take a look at the output here in Katello:

irb(main):001:0> Host.first
Hirb Error: undefined method `gsub' for 2:Integer
</rep>

Where's that coming from?

<pre>
irb(main):006:0> Host.first.content_facet_attributes.to_s
=> 2
irb(main):007:0> Host.first.content_facet_attributes.to_s.is_a?(String)
=> false
</pre>

Foreman should use a method that returns string as a last resort.