[Trivial] Log when order with unknown appData is placed (#2181)

# Description
It is our intention to forbid orders which provide an appDataHash which
we cannot load the pre-image for (as users may later claim they
specified meta-intents such as pre and post hooks, without the protocol
being able to send them to solvers.

Before we do that, we want to make sure we are not breaking existing
implementations.

# Changes
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- [ ] Add a log for whenever an order with an appData hash which we
cannot find (and therefore for now assume the default AppData for) is
placed.

## How to test
CI

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## Related Issues

Fixes #
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crates/shared/src/order_validation.rs

@@ -545,6 +545,7 @@ impl OrderValidating for OrderValidator {
                 let protocol = if let Some(full) = full_app_data_override {
                     validate(full)?.protocol
                 } else {
+                    tracing::warn!(hash = hex::encode(hash.0), "Unknown appData pre-image");
                     ProtocolAppData::default()
                 };