Create REST Endpoint `GET:adsense-links` for `Analytics_4` module

[tofumatt]

Feature Description

Using the code added in #8045, we need to create a REST Route in our WordPress REST API Routes in the Analytics module for fetching AdSense accounts linked to Analytics accounts from the Google Analytics API.

---

Do not alter or remove anything below. The following sections will be managed by moderators only.

Acceptance criteria

• A new data point GET:adsense-links should be added to the Analytics_4 module.
• It should take a GA4 Property ID as parameter and return the links between the provided GA4 property and AdSense account. ie. Google_Service_GoogleAnalyticsAdmin_GoogleAnalyticsAdminV1alphaAdSenseLink[]
• If should not be shareable.

Implementation Brief

• [x] Once the required infrastructure is in place via #8084, we will have Google\Site_Kit\Modules\Analytics_4\GoogleAnalyticsAdmin\PropertiesAdSenseLinksService and a service (TBD. ie. analyticsadsenselinks).
• [x] In Google\Site_Kit\Modules\Analytics_4 class:
  • [x] In get_datapoint_definitions() method, add GET:adsense-links datapoint with the aforementioned service.
  • [x] In create_data_request() method, add a case for the above datapoint:
    • [x] If $data['propertyID'] is not set, return with a missing_required_param error.
    • [x] Otherwise, get the analyticsadsenselinks service and return $analyticsadmin->properties_adSenseLinks->listPropertiesAdSenseLinks( $parent ), where the $parent should be the normalized property ID. ie.self::normalize_property_id ($data['propertyID'] ).
  • [x] In parse_data_response() method, add a case for the above datapoint:
    • [x] Return (array) $response->getAdsenseLinks().

Test Coverage

• Add PHPUnit test coverage for the newly added datapoint.

QA Brief

• Connect the currently used GA4 property with an AdSense account.
• Visit Site Kit
• Run the following JS snippet in the console and verify that the connected AdSense accounts' client id is being returned inside the response.

  const propertyID = googlesitekit.data.select('modules/analytics-4').getPropertyID();
  await googlesitekit.api.get( 'modules', 'analytics-4', 'adsense-links', {propertyID}, {useCache: false});

• The result should be of the following shape:

  [
  {
      "name": "properties/285******/adSenseLinks/5*********",
      "adClientCode": "ca-pub-346*************"
  }
  ]

Changelog entry

• Create REST endpoint to fetch Analytics AdSense links.

[techanvil]

IB :white_check_mark:

[ivonac4]

Adding this one to Sprint 119 since the dependency (8045) is in the CR, so it can at least be started.

[mohitwp]

QA Update ✅

• Tested on dev environment.
• Verified the code snippet mentioned under QAB.
• Verified that the connected AdSense accounts' client id is being returned inside the response.