Fix JSON marshalling for TPM 2.0 digests

[orangecms]

This is what it looks like as of now:
fiedka/fiedka@8eb18d0#diff-37dfadeb85117fdfb03addf286bc6002bfac2f93091f7595e1a5b8d39093c199R11

It appears that marshalling heterogeneous data structures in Go is a bit involved. I'm trying to see how it can be done at all.
There is a corresponding TODO: 6e61994#diff-be86e8a168afe2b653da62f7d8f9d44c907b55446fb34edb49ff861c01662e7cR143

[orangecms]

It should be like this:

{
  "data": "R\u00001\u0000B\u0000E\u0000T\u00006\u00000\u0000W",
  "digests": [
    {
      "algorithm": "SHA1",
      "digest": "3442feda234..."
    }
  ],
  "type": "EV_S_CRTM_VERSION"
}

Currently: "digests": "{}" - so yea, instead of a map of string to string, it needs to be a map of string to number|string|boolean|array|object, as JSON defines, but Go doesn't have unions. I read that some people use interfaces to mimic that. However, that isn't really yet the full solution AFIUI. I tried various things including map[string]json.RawMessage, but I couldn't figure it out.

[orangecms]

I have a "solution" 😨