Show working copy links based on backend actions

[wesleybl]

• I signed and returned the Plone Contributor Agreement, and received and accepted an invitation to join a team in the Plone GitHub organization.
• I verified there aren't other open pull requests for the same change.
• I followed the guidelines in Contributing to Volto.
• I succesfully ran code linting checks on my changes locally.
• I succesfully ran unit tests on my changes locally.
• I succesfully ran acceptance tests on my changes locally.
• If needed, I added new tests for my changes.
• If needed, I added documentation for my changes, either in the Storybook or narrative documentation.
• I included a change log entry in my commits.

---

If your pull request closes an open issue, include the exact text below, immediately followed by the issue number. When your pull request gets merged, then that issue will close automatically.

Closes #5284

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[davisagli]

@plone/volto-team I think this change can be reviewed and merged independently from the other PRs related to supporting working copies for the Plone site. It's updating the logic for when Volto displays the checkin/checkout actions in the More menu, so that it's based on the @actions endpoint.

[stevepiercy]

Use a more appropriate admonition of versionremoved, not deprecated. Otherwise some minor wording and style fixes. I'll commit them.

[stevepiercy]

Docs LGTM now. I'll double-check the PR preview build.

[stevepiercy]

I lied. There is a build error in RTD that appears to be this recently reported issue, and a release is pending. Something for y'all to watch out for in your builds.

nodejs/corepack#612

See the build log for error message.

https://app.readthedocs.org/projects/volto/builds/26990887/

[stevepiercy]

We can ignore the failing readme linkcheck. https://2021.ploneconf.org/ is not returning a 500 ISE, although this is not the first time it has done so.

[stevepiercy]

I checked out this PR, built the docs, and made one more change. The docs look good now.

[wesleybl]

@plone/volto-team I think this change can be reviewed and merged independently from the other PRs related to supporting working copies for the Plone site. It's updating the logic for when Volto displays the checkin/checkout actions in the More menu, so that it's based on the @actions endpoint.

@davisagli would it be good to remove Closed #5284 from the issue description?

[davisagli]

@wesleybl Not necessarily... I merged the PRs for plone.app.iterate and plone.restapi this morning, so this is the remaining one to finish that issue.

[mauritsvanrees]

I can't comment on the technical side of this PR. But I tried it out and it works.

[sneridagh]

LGTM!

[sneridagh]

We could unify this into the main tests then, but it does not hurt to have them separated.