EES-4913 Allow preview access to Public API data sets

[benoutram]

This PR adds preview access to Public API data set version data using preview tokens.

A preview token can be set for a request using a HTTP request header Preview-Token.

It makes a change to the two authorisation handlers associated with the guards IUserService.CheckCanQueryDataSetVersion and IUserService.CheckCanViewDataSetVersion. They now ensure a valid preview token is present in the request before succeeding where they would have otherwise failed due to the version being in an inaccessible status.

A preview token is valid for the DataSetVersion in the context of the request if there exists a PreviewToken entity with matching Id, which is not expired, and the token has been issued for the same DataSetVersion which must also be in Draft status.

Example usage

Get a data set version

GET http://localhost:5050/api/v1.0/data-sets/3d369101-f7e9-2f72-a8fa-64e1717cd5eb/versions/1.0
Preview-Token: 3f369101-4f36-8774-a183-04910906b704

Get a data set version's changes

GET http://localhost:5050/api/v1.0/data-sets/3d369101-f7e9-2f72-a8fa-64e1717cd5eb/versions/1.0/changes
Preview-Token: 3f369101-4f36-8774-a183-04910906b704

Get a data set’s metadata

GET http://localhost:5050/api/v1.0/data-sets/3d369101-f7e9-2f72-a8fa-64e1717cd5eb/meta?dataSetVersion=1.0
Preview-Token: 3f369101-4f36-8774-a183-04910906b704

Query a data Set

Example for (POST) method but preview tokens can also be used to query a data set (GET).

POST http://localhost:5050/api/v1.0/data-sets/3d369101-f7e9-2f72-a8fa-64e1717cd5eb/query?dataSetVersion=1.0
Content-Type: application/json
Preview-Token: 3f369101-4f36-8774-a183-04910906b704

{
  "criteria": {
   "filters": {
      "in": ["IfDbB"]
    },
    "geographicLevels": {
      "eq": "LA"
    },
    "locations": {
      "in": [
        {
          "level": "LA",
          "id": "QgWPw"
        }
      ]
    },
    "timePeriods": {
      "gte": {
        "period": "2022/2023",
        "code": "AY"
      }
    }
  },
  "indicators" : ["enrolments"]
}