History Network: Task list for (somewhat?) "feature completeness"

[kdeme]

This isssue is to track the list of items to specify and implement before we can say that the History Network is "feature complete".

As you will see, it is mostly about providing functionality so that the already existing content types can all be verified as part of the canonical chain.

Not all of these items are actually tasks for the history network itself. Some are to be provided by the Portal beacon network. For most of these specifications need to be added/updated still and some further research might/will be required.

• [ ] Have a functional Portal beacon network: Required to be able to do beacon LC sync to be able to follow the head of the chain.
• [x] Provide the historical_summaries field of the BeaconState with its proof on the Portal beacon network: Required for proving historical headers (> ~27h ) to be canonical. Requires to resolve / decided on #253
• [ ] Add the fixed/static historical_roots into the clients: required to be able to do the same as above but for headers pre Capella. Or/and also provided it over the network with proof: https://github.com/ethereum/portal-network-specs/pull/287
• [ ] Add way to verify latest headers (< ~27h or in current period). These would/could be provided with a temporary proof. The proof or the whole object would be ephemeral and gets updated once a new period occurs. See also issue: https://github.com/ethereum/portal-network-specs/issues/239 & PR https://github.com/ethereum/portal-network-specs/pull/292
• [ ] Adjust the HeaderWithProof content type to accomodate for proofs post merge, proofs post capella, and proofs for recent headers: https://github.com/ethereum/portal-network-specs/pull/287 and https://github.com/ethereum/portal-network-specs/pull/291
• [ ] Adjust bridges to be able to gossip all of the above into the network.

Once all that is done, we should be able to gossip latest and all older headers, bodies and receipts into the network and also verify those.

Further (performance) improvements are not really part of this issue to track but might pop-up as we continue to fill up the current network.