[DRAFT] Spenderlog integration

[madsnedergaard]

This is an initial draft for creating an integration with Spenderlog.

There's still a bunch of stuff to be done:

• This integration gets co2 calculations directly from Spenderlog - I don't know the best way of handling that
• We need categories from their API - this requires further talk with their team

Data examples

The entries look like this:

[
  {
      "date": "2020-01-01",
      "category_id": 6,
      "value": "1.860"
   }
]

[madsnedergaard]

I couldn't find a way to change this PR to a draft PR, so I created a new one 😅