Fetch the policy constants

{
  "data": {
    "stakingContractAddress": "string",
    "coinbaseAddress": "string",
    "transactionValidityWindow": 0,
    "maxSizeMicroBody": 0,
    "version": 0,
    "slots": 0,
    "blocksPerBatch": 0,
    "batchesPerEpoch": 0,
    "blocksPerEpoch": 0,
    "validatorDeposit": 0,
    "minimumStake": 0,
    "totalSupply": 0,
    "blockSeparationTime": 0,
    "jailEpochs": 0,
    "genesisBlockNumber": 0
  },
  "metadata": null
}