[Next.js] [BYOC] Component Builder integration endpoint

[illiakovalenko]

• This PR follows the Contribution Guide
• Changelog updated

Description / Motivation

Added a new endpoint to enable Component Builder to work with BYOC components registered in a JSS application

• The FEAASRenderMiddleware ( /api/editing/feaas/render) will

  1. Enable Next.js Preview Mode.
  2. Redirect to the /feaas/render page.

NOTE: Handles Vercel protection bypass, custom server url etc.

If "src" query parameter is provided, the page will render a FEAAS component.
The page provides all the registered FEAAS components

• The FEAASRender (/feaas/render) page is responsible for

  1. Rendering the FEAAS component if the "feaasSrc" is provided.
  2. Rendering all the registered components.
  3. The page is rendered only if it's requested by the api route (/api/editing/feaas/render) using the preview mode.

• Introduced a common RenderMiddleware

Testing Details

• Unit Test Added
• Manual Test/Other (Please elaborate)

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)

[ambrauer]

Looking good! See some comments

[ambrauer]

Looks good to me.
One last thought is if we want to include this under "editing" or not. Maybe we should do "/api/feaas/render" (or "/api/feaas/preview") instead and leave "editing" dedicated to our Pages/EE editing integration?
Although you are using the "editing" debug namespace so would probably need to switch that.
I could be convinced either way :)