Vendor code from plone.app.layout to avoid direct dependency on Classic UI

[davisagli]

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📚 Documentation preview 📚: https://plonerestapi--2020.org.readthedocs.build/

[mister-roboto]

@davisagli 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!

[davisagli]

@jenkins-plone-org please run jobs

[petschki]

LGTM

[jensens]

Hmm, wouldnt it be better to have one source of truth used by both, plone.app.layout and plone.restapi - deeper in the core then. Actually I am not sure where. But this smells a bit.

[petschki]

That would be great, but I think its not easy because restapi is compatible with Plone 5.2 - 6.2

[davisagli]

@jensens Yeah, I think you are right. Maybe they should go in CMFPlone?

@petschki is right that we still try to keep compatibility with Plone 5, but we can use conditional imports for that.

[ale-rt]

Also to me this looks like something that should belong to Products.CMFPlone.