[Bridge] Would be nice if ExtraMemo was not required in order to do compliance

[Mr0grog]

In writing the new anchor guide, I was at first a little confused to find that I had to specify extra_memo in the payment parameters to the bridge server in order to trigger usage of the compliance server (in my first several attempts, I had left it empty and couldn’t figure out why I wasn’t seeing any compliance activity).

After looking through the source, I definitely understand that using extra_memo as a shorthand prevents hitting the receiver’s stellar.toml (especially since the compliance server will do it again), but from a user perspective, this still seems a little awkward. Maybe the compliance server could respond with a special status code to indicate that no compliance was necessary or maybe the bridge server could pass along the foreign stellar.toml data?