Make htlc_minimum_msat configurable

Instead of computing dynamically htlc_minimum_msat based on feerate,
relies on user-provided configuration value. This let user compute
an economical-driven channel parameter according to network dynamics.

Author: Antoine Riard

lightning/src/ln/channel.rs

@@ -433,10 +433,6 @@ impl<ChanSigner: ChannelKeys> Channel<ChanSigner> {
 		cmp::max(at_open_background_feerate * B_OUTPUT_PLUS_SPENDING_INPUT_WEIGHT / 1000, 546) //TODO
 	}
 
-	fn derive_our_htlc_minimum_msat(_at_open_channel_feerate_per_kw: u64) -> u64 {
-		1000 // TODO
-	}
-
 	// Constructors:
 	pub fn new_outbound<K: Deref, F: Deref>(fee_estimator: &F, keys_provider: &K, their_node_id: PublicKey, channel_value_satoshis: u64, push_msat: u64, user_id: u64, logger: Arc<Logger>, config: &UserConfig) -> Result<Channel<ChanSigner>, APIError>
 	where K::Target: KeysInterface<ChanKeySigner = ChanSigner>,
@@ -519,7 +515,7 @@ impl<ChanSigner: ChannelKeys> Channel<ChanSigner> {
 			their_max_htlc_value_in_flight_msat: 0,
 			their_channel_reserve_satoshis: 0,
 			their_htlc_minimum_msat: 0,
-			our_htlc_minimum_msat: Channel::<ChanSigner>::derive_our_htlc_minimum_msat(feerate),
+			our_htlc_minimum_msat: 1,
 			their_to_self_delay: 0,
 			our_to_self_delay: config.own_channel_config.our_to_self_delay,
 			their_max_accepted_htlcs: 0,