Changing default "<response>" and "<item>" tags in XML export

changes to improve functionality and code:

• I needed some more elements inside the root node, so I introduced an additional config field called "metadata" as a textarea
• also, I replaced the custom replacement of {{ lang }} by allowing the use of token in the attributes and metadata fields
• additionally I switched to dep. inj. where possible

still left to do:

• instead of strpos and str_replace, switch to a better way of manipulating the XML (i.e. using DOMDocument)

The code in #47 and in the MR need to be reconciled. It would also be great to add a batch export test for these custom xml tags.

The #47 has one issue.
If you open the settings of the data export format with enabled warning logging ($config['system.logging']['error_level'] = 'verbose';) you will get a warning "Warning: Undefined array key "metadata" in /var/www/html/web/modules/contrib/views_data_export/src/Plugin/views/style/DataExport.php on line 241".

I have updated the #47 patch to fix this warning.

Thank you very much the path #50 work well!

how to add attributes to Item node name?
can this be done via the API?

#50 works also.

I would suggest to move the "Item wrapper node name" before "Item node name" configuration field.

Hello,

I am not seeing the drop down info for the xml settings. however, I do see it for the CSV settings.

#50 works

The XML configuration worked in my environment

#50 works +1

This looks great, and thanks for the hard work everyone, but this sort of change really should have some tests to make sure we're not breaking things for existing sites, and that the new settings work correctly etc. so setting back to needs work.