add posts scope filter

app/services/posts_query_resolver_service.rb

@@ -0,0 +1,22 @@
+class PostsQueryResolverService
+  attr_reader :filter, :current_user
+
+  def initialize(filter, current_user)
+    @filter = filter
+    @current_user = current_user
+  end
+
+  def self.call(filter, current_user)
+    new(filter, current_user).call
+  end
+
+  def call
+    scope = Post.all
+
+    if filter[:scope] == 'follows' && current_user
+      scope = scope.by_user_follows(current_user)
+    end
+
+    scope
+  end
+end