fix: don't assume required pagination in actions means relationships …

…are paginated

It would be a breaking change to assume that if the destination action is
paginated that we must use pagination for that relationship.

This may, unfortunately, break some clients that were relying on this
behavior. Specifically, anyone with required keyset pagination on
their primary read actions. There is not much I can do to address that.

For affected users: use the `paginate_with` option, or set this config
in config.exs:

```elixir
config :ash_graphql, :required_pagination_extends_to_relationships
```

I'm not documenting that configuration for now because I don't think
that it should be the default behavior. Too "spooky action at a distance"
to modify the relationship resolvers when editing actions. It doesn't
even work that way in Ash core.

lib/resource/resource.ex

@@ -1564,8 +1564,12 @@ defmodule AshGraphql.Resource do
 
   defp pagination_strategy(strategy, action, allow_relay?) do
     strategies =
-      if action.pagination.required? do
-        []
+      if Application.get_env(:ash_graphql, :required_pagination_extends_to_relationships, false) do
+        if action.pagination.required? do
+          []
+        else
+          [nil]
+        end
       else
         [nil]
       end