SimpleFIN integration

[boehs]

See actualbudget/actual#2272

SimpleFIN supports investments as well with its integration. Really simple API documented here: https://www.simplefin.org/protocol.html. Unfortunately the investment support isn't documented there, but it's simple enough, this is a sample:

{
  "org": {
    "domain": "www.fidelity.com",
    "name": "Fidelity Investments",
    "sfin-url": "https://beta-bridge.simplefin.org/simplefin",
    "url": "https://www.fidelity.com",
    "id": "www.fidelity.com"
  },
  "id": "censored",
  "name": "Brokerage",
  "currency": "USD",
  "balance": "100000.00",
  "available-balance": "0.00",
  "balance-date": 1735938469,
  "transactions": [
    {
      "id": "censored",
      "posted": 1735819200,
      "amount": "5000.00",
      "description": "CHECK RECEIVED (Cash) Cash",
      "payee": "Check Received Cash",
      "memo": "",
      "transacted_at": 1735819200
    },
    {
      "id": "censored",
      "posted": 1730376000,
      "amount": "-10000.00",
      "description": "YOU BOUGHT VANGUARD INDEX FUNDS S&P 500 ETF USD (VOO) (Cash) Cash",
      "payee": "Vanguard",
      "memo": "",
      "transacted_at": 1730376000
    },
  ],
  "holdings": [
    {
      "id": "censored",
      "created": 1734719509,
      "currency": "",
      "cost_basis": "90000.00",
      "description": "VANGUARD INDEX FUNDS S&P 500 ETF USD",
      "market_value": "100000.00",
      "purchase_price": "0.00",
      "shares": "100.03",
      "symbol": "VOO"
    },
  ]
}

edit: I have no affiliation with SimpleFIN aside from using their product. The actual maintainers say good things about the author of the product but I haven't personally interacted with them.