panic potential: htlc_accepted hook may have some fields not set

[JssDWt]

The following fields might not be set in the htlc_accepted hook:

greenlight/libs/gl-plugin/src/lsp.rs

Lines 18 to 23 in 2cd4d07

	forward_msat: Amount,
	outgoing_cltv_value: u32,
	#[serde(deserialize_with = "from_hex")]
	shared_secret: Vec<u8>,
	#[serde(deserialize_with = "from_hex")]
	next_onion: Vec<u8>,

These should all be wrapped in Option<_>

unwrap is called on deserialization here: https://github.com/JssDWt/greenlight/blob/5dc32eb0d7163c5946cd9f58e698168fd0a1652d/libs/gl-plugin/src/lsp.rs#L55

This may cause panicks deserializing the htlc_accepted payload.