Displays validation error messages on control panel forms

[wesleybl]

Fixes: #5274

Now the error is displayed:

To works properly, it needs: plone/plone.restapi#1771

But it can be merged separately without any problems.

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[davisagli]

Could you resolve the merge conflict?

[wesleybl]

@ichim-david I ran into the error in the "As editor, I can unlock a locked page" test again. I remember you found a solution to the problem:

#5933 (comment)

Do you intend to make this fixe?

[wesleybl]

Could you resolve the merge conflict?

@davisagli done.

[ichim-david]

@ichim-david I ran into the error in the "As editor, I can unlock a locked page" test again. I remember you found a solution to the problem:

#5933 (comment)

Do you intend to make this fixe?

@wesleybl yup I do ... time to dust up the old pull request I didn't add, April was not a good month for Volto work unlike March :)

[ichim-david]

@ichim-david I ran into the error in the "As editor, I can unlock a locked page" test again. I remember you found a solution to the problem:

#5933 (comment)

Do you intend to make this fixe?

@wesleybl only left it there for 1 month .. if you would like to test it locally the locking test here is the pull request where I made the changes necessary to avoid errors after running it 20 times in a row as I've given you the comment on how todo it
#5998

[wesleybl]

@davisagli @sneridagh can you take a look please?

[sneridagh]

@wesleybl what's left of this one?

[wesleybl]

@wesleybl what's left of this one?

@sneridagh I think it's ready to merge. There was a conflict but I resolved it.

[sneridagh]

@wesleybl is p.restapi returning html as error? Where? It's wrong, and should be fixed, at least file an issue.

[wesleybl]

@sneridagh In fact, I only saw restapi return html when we used

debug-exceptions = on

in buildout. To see: plone/plone.restapi#1734

But perhaps this is an extreme case that is not even worth considering.

I just followed the way it is done when validating content forms:

volto/packages/volto/src/components/manage/Add/Add.jsx

Lines 178 to 180 in 6f18663

	const error =
	new DOMParser().parseFromString(message, 'text/html')?.all[0]
	?.textContent || message;

I also don't quite understand why this code is necessary. In my opinion it can be removed.

Perhaps @avoinea can explain why this is necessary, since he was the one who implemented the original code in:

0782a50#diff-0356a7af508f860d87802dfa2b06d502aaed9cd60b130e57740806bd956be87e

[wesleybl]

@sneridagh I answered your questions. Can you take another look please?

[davisagli]

@wesleybl Thanks for your work on this -- and I'm sorry it took me so long to review it.