[5.4] Deprecating UCM code

[Hackwar]

Summary of Changes

The UCM system was added in Joomla 3.2.0 and already at that time had major flaws. In 12 years of development, it hasn't been extended in any way and instead we've rather reduced it instead. (The content versioning was a part of it and has been made standalone in 4.0.) I think it can be said that the concept (which barely exists to start with) has failed and we should remove the remnants of it. This PR deprecates all UCM classes that I could find. It also removes the code where we are using the UCM classes in a functional way. For the moment it keeps it, where it might be used by third party code to keep it backwards compatible. This means that we keep this code in the batch methods, where $this->contentType and $this->type is set with this code, even though neither of the two attributes are used anywhere. We could remove this in 6.0 and drop everything in 7.0 finally.

Testing Instructions

• Add and remove tags from a content item like an article and see no change between before and after applying the patch.
• See the ordering field in forms like from contacts and articles and they also should behave identical between before and after applyting the patch.

Link to documentations

Please select:

• [ ] Documentation link for docs.joomla.org:

• [X] No documentation changes for docs.joomla.org needed

• [X] Pull Request link for manual.joomla.org: https://github.com/joomla/Manual/pull/484

• [ ] No documentation changes for manual.joomla.org needed

[rdeutz]

Our Backward Compatibility Policy states: Advice on how to amend code that is currently using an element that is marked as deprecated MUST be added to the documentation.

This is being tackled from the wrong side.

[Hackwar]

The comment from Robert has been adressed with the latest changes. Yes, I still need to add the documentation... Still, it is ready to be tested. :-)

[Hackwar]

Documentation is also added. Now we need tests. 😃

[exlemor]

I have tested this item :white_check_mark: successfully on bebabfaa964cbc05fda86634d57772ddd18a6eb0

I have successfully tested this successfully.

Both the forms and the Tags were fine BEFORE and AFTER. For the tags, I had 1st level tags, some assigned to both languages, some assigned to only one language, and some 3 levels down in a Tag --> Sub-Tag --> Sub-Sub-Tag.

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[dautrich]

I have tested this item :white_check_mark: successfully on bebabfaa964cbc05fda86634d57772ddd18a6eb0

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[richard67]

RTC

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[richard67]

Thanks all (author and testers).