Remove AssociationInjector instances from components

[hudson-newey]

We have a lot of code that creates models inside components.

Because abstract models require an AssociationInjector to use associations, we have historically been using the injector provided by the components constructor.

This is a code smell because most or all of these models should be created through a service that provides the injector when it is created.

We should audit where we are using an AssociationInjector or Injector inside the components and refactor them out to a service if possible.

This problem was originally identified when we strongly typed the AssociationInjector in #2165 (comment)