[R-1] Enable users to seamlessly set up conversion tracking, without having to set up merchant center first or requiring campaign creation

[ankitrox]

Changes proposed in this Pull Request:

Make improvements to ads conversion tracking experience, including the ability to set-up conversion tracking without needing to complete full onboarding flow

Users should be able to connect to Google ads account in step-1 of the onboarding flow.

Closes #2215.

Detailed description

Current Issue

In the current onboarding journey, user has to go through the Merchant Account center setup in order to connect to the ads account which will eventually setup the conversion tracking. This creates a dependency between ads and merchant account which should not be the case and user should be able to setup conversion tracking without having to setup the merchant account.

Changes in the PR

1. Moved the Google Ads card component from step 4 of the onboarding journey to step 1 of the onboarding journey.
2. Placed the Google Ads card component after Google account card and before Merchant Center card component.
3. Google Ads and Merchant account cannot be connected till jetpack and Google accounts are connected.
4. However; Google ads and MC account card are decoupled from each other; meaning ads or merchant account can be created before/after the other one.
5. Users would require all accounts to be connected in step-1 of the onboarding journey in order to proceed to the next step.

Screenshots:

Detailed test instructions:

1. Start onboarding journey with Marketing > Google Listing & Ads > Start listing products
2. In the step-1 of the onboarding journey, you should be able to view 4 cards
   a. Jetpack
   b. Google
   c. Google Ads
   d. Google Merchant Center
3. Until Jetpack and Google accounts are not connected, Ads and MC cards should stay in disabled state. User should not be able to connect to ads or MC if the Jetpack and Google accounts are not connected.
4. Once Jetpack and Google accounts are connected, Google ads and MC cards should be enabled. If there are existing ads account, you should be able to see dropdown with those accounts. If no existing accounts, there should be "Create Account" button, which would create an ads account.
5. Once the Ads account is successfully connected, there would be a message in ads card component stating "Conversion measurement has been set up. You can create a campaign later.". Please refer following screenshot.
6. You should be able to connect to MC account before Ads account and vice versa.

Changelog entry

Add - Google Ads account invitation acceptance step to the connection process.
Update - Move the Google Ads account connection process from step 4 to step 1 of the onboarding flow.
Update - Enable users to seamlessly set up conversion tracking, without having to set up merchant center first or requiring campaign creation.

[codecov]

Codecov Report

Attention: Patch coverage is 92.30769% with 2 lines in your changes are missing coverage. Please review.

Project coverage is 62.2%. Comparing base (d678ed7) to head (24c494e).
Report is 141 commits behind head on develop.

❗ Current head 24c494e differs from pull request most recent head dfd4075

Please upload reports for the commit dfd4075 to get more accurate results.

Additional details and impacted files

@@             Coverage Diff             @@
##             develop   #2205     +/-   ##
===========================================
- Coverage       64.5%   62.2%   -2.3%     
+ Complexity      4252    4209     -43     
===========================================
  Files            458     748    +290     
  Lines          18041   21615   +3574     
  Branches           0     533    +533     
===========================================
+ Hits           11634   13436   +1802     
- Misses          6407    7727   +1320     
- Partials           0     452    +452     

Flag	Coverage Δ
js-unit-tests	53.9% <ø> (?)
php-unit-tests	63.9% <92.3%> (-0.6%)	⬇️

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

Files	Coverage Δ
js/src/components/account-card/index.js	100.0% <ø> (ø)
src/API/Google/Merchant.php	100.0% <100.0%> (ø)
src/Ads/AccountService.php	98.2% <100.0%> (+0.1%)	⬆️
src/MerchantCenter/AccountService.php	98.2% <100.0%> (+0.1%)	⬆️
src/Options/AdsAccountState.php	0.0% <0.0%> (ø)
src/Options/MerchantAccountState.php	0.0% <0.0%> (ø)

... and 318 files with indirect coverage changes

[joemcgill]

Thanks @ankitrox. I think this is getting close. The main thing that needs updating is the API handling for linking the Ads and MC accounts and updating PHPUnit and E2E tests. I've taken a pass at getting most of this working in #2223. Feel free to merge those into this branch if you'd like and handle additional test updates here.

No longer applicable

[joemcgill]

Now that #2270 is approved an merged, everything in this branch should be ready for final review/merge into develop. E2E tests for this whole branch have been updated in #2308.

cc: @MatthiasReinholz

[eason9487]

Change the merge base to the new feature branch feature/seamlessly-conversion-tracking as there will be other PRs to be added. Continuing to stack more PRs onto this PR is not ideal.

I will be merging this PR. The subsequent PRs will also use the feature/seamlessly-conversion-tracking as their merge base.