#6050596 Themes: update theme install flow

This updates the flow eligibility flow for users that click “Install Theme” on the Theme Showcase.

All users:

• There should be a formatted header and “Install Theme” headercake

For Jetpack and Atomic users:

• the flow should be unchanged

For Simple Site users on an Atomic-eligible plan:

• they should see an eligibility warning, along with a greyed-out upload dropzone
• clicking “continue” should dismiss the warning and activate the dropzone
• the rest of the flow is unchanged

For Simple Site users not on an Atomic-eligible plan:

• they should see a Business plan nudge
• after Checkout, they should be redirected to the Install Theme page with a success notice
• they should now see the eligibility warning, along with a greyed-out upload dropzone
• clicking “continue” should dismiss the warning and activate the dropzone
• the rest of the flow is unchanged

Before:	After:

To test:

On a simple site with a Free, Personal, or Premium plan:

• navigate to Appearance > Themes and click the “Install Theme” button in the top right
• verify that you see a nudge for the Business plan over a greyed-out (and disabled) drop-zone
• click the nudge and purchase a business plan in Checkout (there’s a monthly option under “edit” in the first step if you’re not sandboxing Store)
• verify that you’re returned to the Install Theme page with a success notice, and that the nudge has been replaced with an Atomic eligibility warning
• click “continue” and then upload a theme to kick off the Atomic process
• if Store was sandboxed for your purchase, the Atomic process will probably fail
• if Store was not sandboxed for your purchase, the Atomic process will happen, but will require a reload on complete

On a simple site with a Business plan:

• visit the “Install Theme” page
• verify that you see the eligibility warning
• click “continue”
• verify that the drop-zone becomes active

On an Atomic or Jetpack site:

• visit the “Install Theme” page
• verify that the drop-zone is active and that uploading a theme installs it on your site