I managed to get this working, quite easy in the end actually. I went through all the documentation to find the AddOutputFilter
directive which is plain simple and actually works with extensions.
The AddOutputFilter directive syntax as stated in the docs for version 2.2 is:
AddOutputFilter filter[;filter...] extension [extension] ...
In my example after the AddOutputFilterByType
directive I added:
AddOutputFilter DEFLATE cache
Hope this helps someone in the future.