Implement deterministic ordering

[anuj452005]

Implement CHT-specific customizations for pyxform update

This PR implements all the CHT-specific customizations needed for the pyxform update, ensuring backward compatibility with existing forms while incorporating the latest features from XLSForm/pyxform.

Changes Made

1. Deterministic Ordering of XML Attributes

• Modified the node() function in utils.py to use sorted(kwargs.items()) instead of the default iteration
• This ensures that XML attributes are consistently ordered alphabetically, regardless of the order they appear in the code
• Regenerating a form XML that has not changed will no longer result in significant diffs due to attribute ordering

2. Instance Tag Values Copying

• Modified the tag attribute handling in utils.py to allow tag attributes to pass through except when the tag attribute matches the element's tag name
• This ensures that instance tag values are properly copied in the generated XML
• Added a test file tests/test_instance_tag_values.py to verify this functionality

3. Language Tag Format

• Added a configuration option in constants.py for language tag format
• Modified the _translation_path method in survey_element.py to support the simplified format (e.g., label::en instead of label::/data/label:en)
• Added a test file tests/test_language_tag_format.py to verify the simplified format is used

4. Empty Label Handling

• Modified the xml_label_and_hint method in survey_element.py to handle empty labels
• This allows forms with empty labels to be processed without errors
• Added a test file tests/test_empty_label.py to verify empty labels are handled correctly

5. Verification of Existing Customizations

• Added tests to verify that custom question types (db:person, db:clinic, etc.) are properly handled
• Added tests to verify that meta sections have the tag="hidden" attribute

Documentation

• Created a comprehensive migration guide in migration.md that explains:
  • The changes made in this PR
  • The benefits of each customization
  • Migration notes for form and application developers
  • Testing instructions

Testing

All tests are passing, including:

• tests/test_deterministic_ordering.py
• tests/test_instance_tag_values.py
• tests/test_language_tag_format.py
• tests/test_empty_label.py
• tests/test_custom_question_types.py
• tests/test_meta_section.py

Note: Some tests in the full test suite may fail due to ODK Validate issues, but these are not related to the implemented features and will be addressed separately.

Benefits

• Maintains backward compatibility with existing CHT forms
• Ensures consistent XML generation for better version control
• Preserves all CHT-specific customizations
• Provides a solid foundation for future updates

This PR addresses all the requirements outlined in the original issue, ensuring a smooth transition to the updated pyxform while preserving all CHT-specific functionality.

[JiyaGupta-cs]

Please reference the issue number