has_many through associations initializing incorrectly

The error first showed up when trying to call a scope on an through association

```ruby
# Organization <=> OrganizationMembership <=> User
Organization.find(1).users.throttle(5)
```

which was throwing the error

```JS
Uncaught error: throttle: undefined method throttle for , parent: - Organization,all,___hyperstack_internal_scoped_find_by,{"id"=>1},*0,users>
```

but only on certain pages!

After some digging, this only happened when the through association was initialized by the through association itself (OrganizationMembership).

What appears to be the problem, is the method `AssocationReflection#add_member`, which is initializing the association collection with the class being the owner (Organization), which it should be the target (User).