Add new metadatav3 field `custody_subnet_count` to `GET node/identity` API

[jimmygchen]

Description

The custody_subnet_count field has been added to MetaDataV3, but we don't return it in the HTTP api yet and should be added:

lighthouse/beacon_node/http_api/src/lib.rs

Lines 2897 to 2913 in ae83901

	metadata: api_types::MetaData {
	seq_number: *meta_data.seq_number(),
	attnets: format!(
	"0x{}",
	hex::encode(meta_data.attnets().clone().into_bytes()),
	),
	syncnets: format!(
	"0x{}",
	hex::encode(
	meta_data
	.syncnets()
	.cloned()
	.unwrap_or_default()
	.into_bytes()
	)
	),
	},

[Gua00va]

Can would like to work on this

[Gua00va]

@jimmygchen how are the getter methods for MetaData struct generated? I see we are using these directly when genrating the API response but can't seem to figure out where these are coming from.

[jimmygchen]

Hi @Gua00va sorry about the delayed response

The getter method are generated using superstruct macros as defined here:

lighthouse/beacon_node/lighthouse_network/src/rpc/methods.rs

Lines 122 to 141 in 9aefb55

	#[superstruct(
	variants(V1, V2, V3),
	variant_attributes(
	derive(Encode, Decode, Clone, Debug, PartialEq, Serialize),
	serde(bound = "E: EthSpec", deny_unknown_fields),
	)
	)]
	#[derive(Clone, Debug, PartialEq, Serialize)]
	#[serde(bound = "E: EthSpec")]
	pub struct MetaData<E: EthSpec> {
	/// A sequential counter indicating when data gets modified.
	pub seq_number: u64,
	/// The persistent attestation subnet bitfield.
	pub attnets: EnrAttestationBitfield<E>,
	/// The persistent sync committee bitfield.
	#[superstruct(only(V2, V3))]
	pub syncnets: EnrSyncCommitteeBitfield<E>,
	#[superstruct(only(V3))]
	pub custody_subnet_count: u64,
	}

The guide I think above explains how it works and how to use them. Let me know if you need any help.

[jimmygchen]

Hi @Gua00va
I'm going to pick this up since we are going to need this soon and we haven't heard back - thanks for your interest though!

[jimmygchen]

Completed in #6827