post
https://{server_url}/{api_key}/eth/v1/beacon/pool/attestations
Submits Attestation objects to the node. Each attestation in the request body is processed individually.
If an attestation is validated successfully the node MUST publish that attestation on the appropriate subnet.
If one or more attestations fail validation the node MUST return a 400 error with details of which attestations have failed, and why.
Attestations are stored in pool and broadcast on appropriate subnet