(feature) Extend the limit on group items to support infinite (just like a user's own feed)

Here's the feedback from the squad leaders on the current situation

Emi: There's a 150 posts hard limit on feeds right now.

Emi: We should workaround something for user's own feeds

Emi: because it seems that people like to scroll to the bottom of their own channel

Mark Harding: own channels is infinite now, newsfeed should be able to copy that logic easily

Emi: ah!, but I think they're mostly complaining about that for their own feeds and groups

Let's verify that there's more than a 150 posts on a user's own channel and then apply those changes to the back end