Avila Gastón

We added #1102 to keep our db small but this breaks the spec. We should remove this logic. Instead, we should be able to serve blob_sidecars up until MIN_EPOCHS_FOR_BLOB_SIDECARS_REQUESTS epochs...

We need this to keep our db small. We will need to change this in the future since this breaks the specs.

Instead of decoding each state to get the `key_state`. Only if state pruning takes more than an epoch on mainnet.

This PR fix a bug when building the block for slot 1. The genesis block does not store the payload_block_hash and we were trying to access to a "null" value....

We should handle keys with no duties to perform because they are not active at the moment.

We should gracefully handle bad requests.

Add support to the Slashing Protection Interchange Format [EIP-3076](https://eips.ethereum.org/EIPS/eip-3076).

Most of the Validator API behavior was tested simulating a local testnet with Kurtosis. We should add some unit tests as well.

We should handle the case where the node is running without validators ,and the first one is added via the Validator API.

We should improve the response messages describing the status of the operation (e.g., imported validator/ repeated validator / invalid password).