Add execution block hashes in chain reorg SSE

[bharath-123]

With gloas, there can be a payload reorg where the beacon block stays the same but the payload associated with the block changes.

It might make sense to add the old and new execution block hashes of the head blocks in the chain_reorg event

[michaelsproul]

This approach is similar to option 3 from:

• Update head event in backwards compatible way #589

[nflaig]

This approach is similar to option 3 from:

• Update head event in backwards compatible way #589

I am not in favor of option 3. there but I think adding new fields to this event is fine as they are distinct from existing fields.

[nflaig]

but the payload associated with the block changes.

what exactly do you mean here? the payload associated with a beacon block will always be the same based on bid.block_hash but a payload reorg can happen where it changes from FULL to EMPTY (or vice versa)

or do you mean we should emit chain_reorg also if a payload reorg happens? in that case I think the meaning of depth becomes overloaded

Maybe it's best if we add a separate event for payload reorgs which is emitted when the beacon block is unchanged and only the payload status / EL head changes.

[michaelsproul]

I think using the same reorg event for block/payload reorgs is OK, so long as we specify that the depth relates only to the beacon block depth.

In a sense the block_hash for an empty slot is the most recently applied payload, the hash of which is easy to obtain from block.signed_execution_payload_bid.message.parent_block_hash.

Is that what you had in mind @bharath-123?