Add default site suggestion when creating a new P2 #7200365

resolves 4796-gh-Automattic/p2

Changes proposed in this Pull Request

This pull request adapts the P2’s “Create Workspace” form to the new design we have for it (see linked issue). One of the biggest changes is the suggestion of an available domain name by default.

Before:

After:

Testing instructions

• Run this branch locally or via the Calypso live branch
• Navigate to /start/p2/p2-site
• Fill in a workspace name
• Ensure a workspace address is automatically suggested
• Click the double arrow icon to request a new suggestion
• Ensure the new suggestion is different to the previous one
• Click on “choose a suggestion” to enter a custom domain
• Enter an existing custom domain, ensure an error is shown and more suggestions to pick from are displayed below
• Enter a non-existing custom domain
• Go back and forth between suggestions and custom domains and look for any odd behaviour you can think of.
• Click on create workspace and ensure the new workspace is created with the final name and domains entered in the form.