Log HTTP 400 at TRACE instead of ignoring it

.. while it's most often bitcoind already knowing about a transaction
already, the error sometimes holds additional information (e.g., not
meeting the mempool min).

Author: tnull

src/tx_broadcaster.rs

@@ -56,11 +56,16 @@ where
 						Err(e) => match e {
 							esplora_client::Error::Reqwest(err) => {
 								if err.status() == StatusCode::from_u16(400).ok() {
-									// Ignore 400, as this just means bitcoind already knows the
+									// Log 400 at lesser level, as this often just means bitcoind already knows the
 									// transaction.
 									// FIXME: We can further differentiate here based on the error
 									// message which will be available with rust-esplora-client 0.7 and
 									// later.
+									log_trace!(
+										self.logger,
+										"Failed to broadcast due to HTTP connection error: {}",
+										err
+									);
 								} else {
 									log_error!(
 										self.logger,