Implement serialization for LSPS5 state types

diff --git a/lightning-liquidity/src/lsps5/msgs.rs b/lightning-liquidity/src/lsps5/msgs.rs
index c45e188..f1ef06d 100644
--- a/lightning-liquidity/src/lsps5/msgs.rs
+++ b/lightning-liquidity/src/lsps5/msgs.rs
@@ -16,6 +16,8 @@ use crate::lsps0::ser::LSPSResponseError;
 
 use super::url_utils::LSPSUrl;
 
+use lightning::ln::msgs::DecodeError;
+use lightning::util::ser::{Readable, Writeable};
 use lightning_types::string::UntrustedString;
 
 use serde::de::{self, Deserializer, MapAccess, Visitor};
@@ -288,6 +290,20 @@ impl From<LSPS5Error> for LSPSResponseError {
 #[derive(Debug, Clone, PartialEq, Eq, Hash)]
 pub struct LSPS5AppName(UntrustedString);
 
+impl Writeable for LSPS5AppName {
+	fn write<W: lightning::util::ser::Writer>(
+		&self, writer: &mut W,
+	) -> Result<(), lightning::io::Error> {
+		self.0.write(writer)
+	}
+}
+
+impl Readable for LSPS5AppName {
+	fn read<R: lightning::io::Read>(reader: &mut R) -> Result<Self, DecodeError> {
+		Ok(Self(Readable::read(reader)?))
+	}
+}
+
 impl LSPS5AppName {
 	/// Create a new LSPS5 app name.
 	pub fn new(app_name: String) -> Result<Self, LSPS5Error> {
@@ -430,6 +446,20 @@ impl From<LSPS5WebhookUrl> for String {
 	}
 }
 
+impl Writeable for LSPS5WebhookUrl {
+	fn write<W: lightning::util::ser::Writer>(
+		&self, writer: &mut W,
+	) -> Result<(), lightning::io::Error> {
+		self.0.write(writer)
+	}
+}
+
+impl Readable for LSPS5WebhookUrl {
+	fn read<R: lightning::io::Read>(reader: &mut R) -> Result<Self, DecodeError> {
+		Ok(Self(Readable::read(reader)?))
+	}
+}
+
 /// Parameters for `lsps5.set_webhook` request.
 #[derive(Debug, Clone, Serialize, Deserialize, PartialEq, Eq)]
 pub struct SetWebhookRequest {
diff --git a/lightning-liquidity/src/lsps5/service.rs b/lightning-liquidity/src/lsps5/service.rs
index 9f0a802..e9a8eff 100644
--- a/lightning-liquidity/src/lsps5/service.rs
+++ b/lightning-liquidity/src/lsps5/service.rs
@@ -23,6 +23,7 @@ use crate::utils::time::TimeProvider;
 
 use bitcoin::secp256k1::PublicKey;
 
+use lightning::impl_writeable_tlv_based;
 use lightning::ln::channelmanager::AChannelManager;
 use lightning::ln::msgs::{ErrorAction, LightningError};
 use lightning::sign::NodeSigner;
@@ -58,6 +59,14 @@ struct Webhook {
 	last_notification_sent: Option<LSPSDateTime>,
 }
 
+impl_writeable_tlv_based!(Webhook, {
+	(0, _app_name, required),
+	(2, url, required),
+	(4, _counterparty_node_id, required),
+	(6, last_used, required),
+	(8, last_notification_sent, option),
+});
+
 /// Server-side configuration options for LSPS5 Webhook Registration.
 #[derive(Clone, Debug)]
 pub struct LSPS5ServiceConfig {
@@ -647,3 +656,7 @@ impl PeerState {
 		self.webhooks.is_empty()
 	}
 }
+
+impl_writeable_tlv_based!(PeerState, {
+	(0, webhooks, required_vec),
+});
diff --git a/lightning-liquidity/src/lsps5/url_utils.rs b/lightning-liquidity/src/lsps5/url_utils.rs
index 139b5e2..c9d5f9e 100644
--- a/lightning-liquidity/src/lsps5/url_utils.rs
+++ b/lightning-liquidity/src/lsps5/url_utils.rs
@@ -11,15 +11,15 @@
 
 use super::msgs::LSPS5ProtocolError;
 
+use lightning::ln::msgs::DecodeError;
+use lightning::util::ser::{Readable, Writeable};
 use lightning_types::string::UntrustedString;
 
 use alloc::string::String;
 
 /// Represents a parsed URL for LSPS5 webhook notifications.
 #[derive(Debug, Clone, PartialEq, Eq, Hash)]
-pub struct LSPSUrl {
-	url: UntrustedString,
-}
+pub struct LSPSUrl(UntrustedString);
 
 impl LSPSUrl {
 	/// Parses a URL string into a URL instance.
@@ -66,17 +66,17 @@ impl LSPSUrl {
 			None => {},
 		};
 
-		Ok(LSPSUrl { url: UntrustedString(url_str) })
+		Ok(LSPSUrl(UntrustedString(url_str)))
 	}
 
 	/// Returns URL length.
 	pub fn url_length(&self) -> usize {
-		self.url.0.chars().count()
+		self.0 .0.chars().count()
 	}
 
 	/// Returns the full URL string.
 	pub fn url(&self) -> &str {
-		self.url.0.as_str()
+		self.0 .0.as_str()
 	}
 
 	fn is_valid_url_char(c: char) -> bool {
@@ -89,6 +89,20 @@ impl LSPSUrl {
 	}
 }
 
+impl Writeable for LSPSUrl {
+	fn write<W: lightning::util::ser::Writer>(
+		&self, writer: &mut W,
+	) -> Result<(), lightning::io::Error> {
+		self.0.write(writer)
+	}
+}
+
+impl Readable for LSPSUrl {
+	fn read<R: lightning::io::Read>(reader: &mut R) -> Result<Self, DecodeError> {
+		Ok(Self(Readable::read(reader)?))
+	}
+}
+
 #[cfg(test)]
 mod tests {
 	use super::*;
@@ -104,7 +118,7 @@ mod tests {
 
 		assert!(result.is_ok());
 		let url = result.unwrap();
-		assert_eq!(url.url.0.chars().count(), url_chars);
+		assert_eq!(url.0 .0.chars().count(), url_chars);
 	}
 
 	#[test]