Connection: Redirect plugins and dashboard connect buttons to the main flow

[tyxla]

Currently, the main connection flow starting from /wp-admin/admin.php?page=jetpack#/ has the connect-in-place flow, but the buttons starting from the WP-admin dashboard (/wp-admin/index.php) and plugins screen (/wp-admin/plugins.php) still work the old way.

This PR updates these buttons so they respect the constant and A/B test, and based on them, redirect to either the original connection flow or the connect-in-place flow.

Changes proposed in this Pull Request:

• Update dashboard and plugins screens connection buttons:
  • Respect the JETPACK_SHOULD_USE_CONNECTION_IFRAME constant.
  • Respect the jetpack_connect_in_place_v2 A/B test.
  • If connect-in-place flow is enabled through the constant or the A/B test, redirect to it and start the flow.
  • If connect-in-place flow is not enabled, the buttons would redirect to the WP.com connection flow, like they used to do before.

Is this a new feature or does it add/remove features to an existing part of Jetpack?

• Part of p1HpG7-7nj-p2

Testing instructions:

• Checkout this branch.
• Build Jetpack npm build.
• Follow the instructions below in the following order. I've separated them in sections for clarity.
• Test the connect in place flow from the Jetpack dashboard
  • Disconnect Jetpack if it was connected.
  • Add this to your wp-config.php: define( 'JETPACK_SHOULD_USE_CONNECTION_IFRAME', true );
  • Go to /wp-admin/admin.php?page=jetpack#/
  • Click the "Set up Jetpack" button.
  • Verify it works the same way as it does on master.
  • Verify you're still able to connect like before.
  • Disconnect Jetpack.
• Test the connect in place flow from the WP admin dashboard
  • Go to /wp-admin/index.php.
  • Click the "Set up Jetpack" button.
  • Verify it redirects to /wp-admin/admin.php?page=jetpack#/setup
  • Verify you see the loading screen, and after a little, you see either the "Approve" button, or the "Connect with WordPress.com" button.
  • Verify you're still able to connect like before.
  • Disconnect Jetpack.
• Test the connect in place flow from the plugins screen
  • Go to /wp-admin/plugins.php.
  • Click the "Set up Jetpack" button.
  • Verify it redirects to /wp-admin/admin.php?page=jetpack#/setup
  • Verify you see the loading screen, and after a little, you see either the "Approve" button, or the "Connect with WordPress.com" button.
  • Verify you're still able to connect like before.
  • Disconnect Jetpack.
• Test the original connection flow from the Jetpack dashboard
  • Remove this from your wp-config.php: define( 'JETPACK_SHOULD_USE_CONNECTION_IFRAME', true );
  • Go to /wp-admin/admin.php?page=jetpack#/
  • Open your Network requests tab.
  • Click the "Set up Jetpack" button.
  • Verify that this performs a request to the A/B test endpoint.
  • Verify you're redirected to the WP.com Jetpack Connect authorization flow.
  • Verify you're still able to connect like before.
  • Disconnect Jetpack.
• Test the original connection flow from the WP admin dashboard
  • Go to /wp-admin/index.php.
  • Open your Network requests tab.
  • Click the "Set up Jetpack" button.
  • Verify that this performs a request to the A/B test endpoint.
  • Verify you're redirected to the WP.com Jetpack Connect authorization flow.
  • Verify you're still able to connect like before.
  • Disconnect Jetpack.
• Test the original connection flow from the plugins screen
  • Go to /wp-admin/plugins.php.
  • Open your Network requests tab.
  • Click the "Set up Jetpack" button.
  • Verify that this performs a request to the A/B test endpoint.
  • Verify you're redirected to the WP.com Jetpack Connect authorization flow.
  • Verify you're still able to connect like before.
• If you got to this point, I wish to thank you for the thorough testing ❤️💪

Proposed changelog entry for your changes:

• Connection: Redirect plugins and dashboard connect buttons to the main flow

[jetpackbot]

Thank you for the great PR description!

When this PR is ready for review, please apply the [Status] Needs Review label. If you are an a11n, please have someone from your team review the code if possible. The Jetpack team will also review this PR and merge it to be included in the next Jetpack release.

Scheduled Jetpack release: October 1, 2019.
Scheduled code freeze: September 24, 2019

Generated by 🚫 dangerJS against 22063d8

[enejb]

I went though and tested the flows and they worked as expected. Thanks for fixing all the minor things I found a long the way.
This is ready to ship

[enejb]

Nicely done.

[tyxla]

Thanks for the review and for testing it Enej 🙌