return `event_index` in Stacks transaction event metadata

Stacks transaction events have an event index that indicates their ordering inside it. They are sent from the Stacks node to RPC listeners like so (see event_index):

    {
      "txid": "0xb55e53065b3e934716eb0f7dcce5138b719ea247459f18f60893e15c8d9a0159",
      "type": "ft_mint_event",
      "committed": true,
      "event_index": 46,
      "ft_mint_event": {
        "amount": "40000000000000",
        "recipient": "SP16KWQY6ZPXNYT43A4RKXBXMFT3V7ZMV5YYNR1CK",
        "asset_identifier": "SP3XYJ8XFZYF7MD86QQ5EF8HBVHHZFFQ9HM6SPJNQ.meme-token::MEME"
      }
    },

However, chainhook payloads do not return these indexes inside events, which makes it impossible to sort them by the order in which they were processed (no event_index here):

{
  "data": {
    "amount": "144",
    "asset_identifier": "SP466FNC0P7JWTNM2R9T199QRZN1MYEDTAR0KP27.miamicoin-token::miamicoin",
    "recipient": "SPCXZRY4FQZQHQ1EMBSDM1183HDK2ZGHPW3M1MA4",
    "sender": "SP3HXJJMJQ06GNAZ8XWDN1QM48JEDC6PP6W3YZPZJ"
  },
  "type": "FTTransferEvent"
}

Could this index be returned with these events? This is necessary for the Token Metadata API to process notifications correctly. Ideally, events should look like this:

{
  "data": {
    "amount": "144",
    "asset_identifier": "SP466FNC0P7JWTNM2R9T199QRZN1MYEDTAR0KP27.miamicoin-token::miamicoin",
    "recipient": "SPCXZRY4FQZQHQ1EMBSDM1183HDK2ZGHPW3M1MA4",
    "sender": "SP3HXJJMJQ06GNAZ8XWDN1QM48JEDC6PP6W3YZPZJ"
  },
  "type": "FTTransferEvent",
  "position": {
    "index": 46,
  }
}

hirosystems / chainhook

return `event_index` in Stacks transaction event metadata #387