Licensing: Move licensing endpoints to package

[ebinnion]

In preparation of moving licensing into the my-jetpack package, this pull request moves the licensing endpoints out of the Jetpack plugin and into the licensing package. This will then allow any consumer of the licensing package to use the endpoints without requiring the Jetpack plugin itself.

Changes proposed in this Pull Request:

• Moves licensing endpoints out of Jetpack plugin into licensing package.

Jetpack product discussion

NA

Does this pull request change what data or activity we track or use?

No

Testing instructions:

Newer licenses flow:

• Checkout PR
• Set define( 'JETPACK_AUTOLOAD_DEV', true ); constant (I think 😄 )
• Go to https://cloud.jetpack.com/pricing and purchase a product
• On next page, scroll to end of site selector and select manual setup
• Click through the next step
• Copy license
• Go to Jetpack dashboard and go to "My Plan" section
• Click "Activate Product" button
• Enter in a key that will fail, such as this_fails
• Verify the key fails as expected and that a successful API response comes back
• Enter in the copied key
• Verify that there are several licensing calls that succeed
• Go to "My Plan" section again and verify that your plan/product shows up

Older partnership license flow:

• Set add_filter( 'jetpack_licensing_ui_enabled', '__return_true' );
• Purchase another key
• Go to "My Plan" section of dashboard
• Enter license key in the input that shows below the list of any existing plans or products
• Verify a successful response
• Wait a few seconds and reload the page
• Verify subscription exists in the list of plans/products

Note: The licensing/user/licenses doesn't appear to actually be used in the plugin? It is used in an action but I don't see that action being used anywhere.

[github-actions]

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Jetpack plugin:

• Next scheduled release: May 3, 2022.
• Scheduled code freeze: April 25, 2022.

[ebinnion]

At this point, the couple of outstanding items that I can think of are moving over tests to the new package and perhaps splitting off the endpoints to their own class.

[jeherve]

Just a quick drive-by, hopefully this helps a bit.

[rcanepa]

LGTM.

I did a quick review of the code changes and they look reasonable to me. Furthermore, I thoroughly tested these flows manually and everything worked as expected.

[ebinnion]

Great! Thank you Renzo. I'll get it rebased and ready for a final review then 🙇‍♂️