## Issue Addressed
Resolves#1809Resolves#1824Resolves#1818Resolves#1828 (hopefully)
## Proposed Changes
- add `validator_index` to the proposer duties endpoint
- add the ability to query for historical proposer duties
- `StateId` deserialization now fails with a 400 warp rejection
- add the `validator_balances` endpoint
- update the `aggregate_and_proofs` endpoint to accept an array
- updates the attester duties endpoint from a `GET` to a `POST`
- reduces the number of times we query for proposer duties from once per slot per validator to only once per slot
Co-authored-by: realbigsean <seananderson33@gmail.com>
Co-authored-by: Paul Hauner <paul@paulhauner.com>