Add scope parameter to /api/search/tags

[joe-elliott]

What this PR does:
This PR

• adds a ?scope parameter to the /api/search/tags endpoint. This parameter can currently take 3 values (resource, span, and intrinsic) as well as no value which defaults to the old behavior of returning both span and resource tags.
• removes attributes that are non-existent in traceql such as root.name and root.service.name.
• Adds a new endpoint /api/v2/search/tags that returns all tags organized by scope.

Note that this PR is blocked by #2244. Marking this as draft until that is merged.

Which issue(s) this PR fixes:
Fixes #2233

Checklist

• Tests updated
• Documentation added
• CHANGELOG.md updated - the order of entries should be [CHANGE], [FEATURE], [ENHANCEMENT], [BUGFIX]

[knylander-grafana]

Thank you for adding documentation! Changes look good. One minor suggestion for a missing comma.

[adrapereira]

Did you consider a new version of the endpoint where you return a list of available scopes for each tag?

For example:
GET /api/v2/search/tags

[
  { tag: "name", scopes: ["intrinsic"] },
  { tag: "http.status_code", scopes: ["span"] },
  { tag: "service.name", scopes: ["resource", "span"] },
  ...
]

The main advantage is that the client only needs to make one request to get all the information about the available tags and what their scopes are. With the solution from this PR a client would always have to perform three requests to get the full picture, one for each scope.

[joe-elliott]

Did you consider a new version of the endpoint where you return a list of available scopes for each tag?

I did, but I liked not revving the endpoint b/c then I had to write less code :). If I did create a v2 it would likely return something like this though:

{
  "intrinsic": [ "array", "of", "strings"],
  "span": [ "a", "b", "c"],
  "resource": [ "d", "e", "f" ],
  ...
}

would you all prefer this?

[adrapereira]

Yes, that also works! Is it possible for a tag to be in more than one scope?

[joe-elliott]

Yes, that also works! Is it possible for a tag to be in more than one scope?

Yup, but this would likely occur rarely.

[joe-elliott]

@adrapereira added a v2 endpoint. Example:

$ curl -G -s http://localhost:3200/api/v2/search/tags  | jq
{
  "scopes": [
    {
      "name": "span",
      "tags": [
        "article.count",
        "http.flavor",
        "http.method",
      ]
    },
    {
      "name": "resource",
      "tags": [
        "k6",
        "service.name"
      ]
    },
    {
      "name": "intrinsic",
      "tags": [
        "duration",
        "kind",
        "name",
        "status"
      ]
    }
  ]
}

[knylander-grafana]

Doc addition looks good. Thank you.

[zalegrala]

Looks good to me, just a couple comments.

[zalegrala]

Nice work. Looks good to me.