[OMP] Language is not included in ONIX export

[kaitlinnewson]

Describe the bug
In the ONIX export in OMP, the <Language> is not being populated in ONIX exports.

To Reproduce
Steps to reproduce the behavior:

1. Go to the ONIX export tool in OMP
2. Export a published submission
3. See that the Language is missing in the XML.

What application are you using?
OMP (all versions)

Additional information

• Forum post
• The ONIX export code where Language should be set in 3.3

[kaitlinnewson]

@bozana PRs ready for review:

• omp 3.3: pkp/pkp-lib#10641 fix onix export language and update title elements omp#1793
• omp 3.4: pkp/pkp-lib#10641 fix onix export language and update title elements omp#1794
• omp main: pkp/pkp-lib#10641 fix onix export language and update title elements … omp#1795

As part of this PR I also fixed issues I found in the title elements, based on the ONIX documentation about prefixes for titles. It specifies:

"<TitleText> – is reserved for use when the sending system cannot differentiate between titles that include a prefix and titles that do not."

... and so I removed usage of the <TitleText> element since we can differentiate the prefix elements.

For the main branch, I also updated UserGroup based on the recent refactor.

[bozana]

Hi @kaitlinnewson, thanks a lot! All merged, thus closing the issue...