Preview page in CMS

[simonrjones]

Allow a CMS editor user to view pages on the frontend from WordPress, both when viewing a published page and when viewing an unpublished draft page (preview).

Dependant on #63

Work
Basic functionality:

• WordPress plugin to view a page in WordPress in the frontend (use API to retrieve frontend URL based on CMS post ID)

Prerequisites for preview functionality:

• Work out a way to auth against WP REST API from an external location (frontend), e.g. https://wordpress.org/plugins/application-passwords/ or https://wordpress.org/plugins/jwt-authentication-for-wp-rest-api/
• Create preview URL for frontend (e.g. preview.domain.com) which serves same content but requires authentication
• Create basic login page for preview URL which should then authenticate. Support two models: 1) CMS (WordPress), 2) stored credentials in .users file (or similar), do not commit to version control
• WordPress API endpoint to return draft content when authenticated by API token

Preview functionality:

• WordPress plugin to preview the current page, "Preview" button which does the following:
  • Saves draft content in WP
  • User visits preview domain URL
  • User logs into preview site (via WordPress)
  • Preview site requests draft content from WordPress API
  • Load Preview content into web page and display to user

[simonrjones]

[simonrjones]

see Netlify's approach to this https://www.netlifycms.org/docs/deploy-preview-links/

[simonrjones]

And WP Engine's approach https://github.com/wpengine/headless-framework/blob/canary/docs/previews/README.md