move template from plone.app.workflow to plone.app.layout

[MrTango]

No description provided.

[mister-roboto]

@MrTango thanks for creating this Pull Request and helping to improve Plone!

TL;DR: Finish pushing changes, pass all other checks, then paste a comment:

@jenkins-plone-org please run jobs

To ensure that these changes do not break other parts of Plone, the Plone test suite matrix needs to pass, but it takes 30-60 min. Other CI checks are usually much faster and the Plone Jenkins resources are limited, so when done pushing changes and all other checks pass either start all Jenkins PR jobs yourself, or simply add the comment above in this PR to start all the jobs automatically.

Happy hacking!

[MrTango]

Since we have some API code in the sharing view, we can't just move it to plone.app.layout.
We need to separate the UI code from the API code.
To do this we will create a new sharing view in plone.app.layout with a plone.app.layout.interfaces.IClassicUI BrowserLayer which subclasses the sharing view from plone.app.workflow and add's the classic UI related parts like the call and handle_form methods. As long as plone.app.layout is available, this will be the view one get's while calling for the sharing view. In Plone 7 plone.app.layout will become optional and when it is not present, one will get the base view in plone.app.workflow with the API related code, instead of the one from plone.app.layout. No code needs to change in plone.restapi.

For addon's overriding the sharing view, they need to update their Browserlayer to subclass from plone.app.layout.interfaces.IClassicUI BrowserLayer.