Made some progress

app/services/follow_service.rb

@@ -0,0 +1,12 @@
+class FollowService
+  def call(source_account, uri)
+    target_account = follow_remote_account_service.(uri)
+    source_account.follow!(target_account)
+  end
+
+  private
+
+  def follow_remote_account_service
+    FollowRemoteAccountService.new
+  end
+end