Enable attester selections from the request

[cowbon]

A new option is now added tp config.yaml, list-options. If it's set to all, ratsd populates the EAT with CMW from all available attesters. If it's set to selected, the user must specify the name of each attester along with the associated options in attester-selection. If the user does not wish to specify the attester-specific option, "$attester_name": "null" should be specified. The following is an example of the request body.

{
  "nonce": "base64urlencoded",

  "attester-selection": {
    "attester-id-1": {
      "param11name": "param11value",
      "param12name": "param12value"
    },
    "attester-id-2": {
      "param21name": "param21value"
    },
    "attester-id-3": null
  }
}

[thomas-fossati]

Thanks for this!

I’ve left a couple of comments inline.

As discussed, there should be accompanying documentation about the options format and the new configuration variable.

[thomas-fossati]

I am probably missing something, but I don’t fully grasp why this should be configuration-defined behaviour, rather than being completely driven by the API user.

[cowbon]

I was trying to implement attester discovery with such config option. In your proposal, you mentioned the user have to specify at least "attester-id": null to include the evidence from attester-id. The option was added to make ratsd behave the same way as the current implementation without this PR. But I'd agree the user may want to perform the discovery first before the query and without restarting ratsd.

[thomas-fossati]

I was trying to implement attester discovery with such config option. In your proposal, you mentioned the user have to specify at least "attester-id": null to include the evidence from attester-id.

Oh, thanks. I forgot I had written that thing 😓

The option was added to make ratsd behave the same way as the current implementation without this PR. But I'd agree the user may want to perform the discovery first before the query and without restarting ratsd.

Perhaps we could leave it in as a temp backstop and remove it when we have implemented proper discovery.