Enable labeling of Ads campaigns

[jorgemd24]

Changes proposed in this Pull Request:

Part of pcTzPl-2nS-p2

We would like to track where campaigns are created from by labeling them with their source of creation. For example, use wc-gla for the web version, and for the mobile versions, something like wc-gla-android or wc-gla-ios.

This PR allows the creation of a new campaign with a specific label. Note that I haven't updated the frontend to send the label query parameter yet, as I would first like to define the label names we'll be using.

Screenshots:

Detailed test instructions:

1. Make the following call POST wp-json/wc/gla/ads/campaigns with this body:

{
    "amount": 0.01,
    "targeted_locations": ["ES"],
    "label": "wc-gla"
}

3. The campaign should be created successfully.
4. Go to https://ads.google.com/
5. Filter your campaign by label:

You should see the campaign that you just created.
6. Alternatively, you can customize the campaigns table to display the labels:

Additional details:

Changelog entry

Add - Enable labeling of Ads campaigns

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 64.9%. Comparing base (f398161) to head (10d296c).

Additional details and impacted files

@@             Coverage Diff             @@
##             develop   #2485     +/-   ##
===========================================
+ Coverage       64.5%   64.9%   +0.4%     
- Complexity      4564    4575     +11     
===========================================
  Files            795     475    -320     
  Lines          22844   17856   -4988     
  Branches        1220       0   -1220     
===========================================
- Hits           14739   11590   -3149     
+ Misses          7938    6266   -1672     
+ Partials         167       0    -167     

Flag	Coverage Δ
js-unit-tests	?
php-unit-tests	64.9% <100.0%> (+0.1%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

Files	Coverage Δ
src/API/Google/AdsCampaign.php	97.2% <100.0%> (+<0.1%)	⬆️
src/API/Google/AdsCampaignLabel.php	100.0% <100.0%> (ø)
src/API/Google/Query/AdsCampaignLabelQuery.php	100.0% <100.0%> (ø)
...rc/API/Site/Controllers/Ads/CampaignController.php	100.0% <100.0%> (ø)
...nal/DependencyManagement/GoogleServiceProvider.php	94.8% <100.0%> (+<0.1%)	⬆️

... and 322 files with indirect coverage changes

[martynmjones]

Hey @jorgemd24, thanks for adding the label functionality 🙌

Confirmed that the label is created and assigned to the campaign.

I left one question but there aren't any issues so LGTM ✅

[martynmjones]

I'm curious why you decided to create the $label_id variable instead of just returning null after the loop?

[jorgemd24]

Yep that's true, it is unnecessary, I removed it here d30851d