Add xs:id and xs:idref resolution

[pahjbo]

📒 Description

This pull request adds support for XML IDREF fields in dataclass models, and adds functionality that is similar to Java's JAXB handling of @XmlID and @XmlIDREF annotations in that when serialising an attribute that is marked as an IDREF, then only ID is emitted, and then when parsing such an XML instance the ID is replaced with the full dataclass instance.

This is related to the discussion item #1221

🔗 What I've Done

I have added two extra metadata items

• at the field level - idref as bool that signifies if the attribute is an xs:IDREF
• at the class Meta level - key as a list[str] that lists the attribute names that when the values are concatenated make up the xs:ID

This second one might seem a little complex, but I have a use case where I need such a thing, and hopefully the unit test example makes this plausible.

Once the data model has been set up, the render and parse are transparent to the caller with the conversion to an xs:ID and the instantiation of the appropriate object happening automatically

💬 Comments

I know that this is an unsolicited new feature, that you might not want to spend time on, but I believe that it is valuable to people with complex XML structures.

There are probably more tests that you might want, but I would need a bit more help with using your harness to do them.
Also If you like the idea, then I can spend some more time on documentation.

🛫 Checklist

• Updated docs
• Added unit-tests - only an "end to end" test - perhaps some of the individual components e.g. IdRefNode could have some tests
• Sample tests pass
• W3C tests pass

[sonarqubecloud]

Quality Gate passed

Issues
2 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud

[codecov]

Codecov Report

❌ Patch coverage is 82.52427% with 18 lines in your changes missing coverage. Please review.
✅ Project coverage is 99.81%. Comparing base (00e6276) to head (595e45c).

Files with missing lines	Patch %	Lines
xsdata/formats/dataclass/parsers/nodes/element.py	69.69%	6 Missing and 4 partials ⚠️
xsdata/formats/dataclass/parsers/nodes/idref.py	84.61%	4 Missing and 2 partials ⚠️
xsdata/formats/dataclass/serializers/mixins.py	92.85%	0 Missing and 1 partial ⚠️
xsdata/utils/testing.py	50.00%	0 Missing and 1 partial ⚠️

Additional details and impacted files

@@             Coverage Diff             @@
##              main    #1222      +/-   ##
===========================================
- Coverage   100.00%   99.81%   -0.19%     
===========================================
  Files          116      117       +1     
  Lines         9376     9478     +102     
  Branches      1439     1462      +23     
===========================================
+ Hits          9376     9460      +84     
- Misses           0       10      +10     
- Partials         0        8       +8     

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