[TASK-957] Add mongo_uuid field to XForm model and populate it

[rajpatel24]

Checklist

1. If you've added code that should be tested, add tests
2. If you've changed APIs, update (or create!) the documentation
3. Ensure the tests pass
4. Run ./python-format.sh to make sure that your code lints and that you've followed our coding style
5. Write a title and, if necessary, a description of your work suitable for publishing in our release notes
6. Mention any related issues in this repository (as #ISSUE) and in other repositories (as kobotoolbox/other#ISSUE)
7. Open an issue in the docs if there are UI/UX changes
8. Create a testing plan for the reviewer and add it to the Testing section

Description

This PR introduces a new field, mongo_uuid, to the XForm model in KoboToolbox. This unique identifier is designed to enhance the ownership transfer process of XForms by ensuring that each form is linked to a distinct UUID in MongoDB. The addition of mongo_uuid will streamline how XForms are managed, especially during ownership transfers, by reducing unnecessary updates to the MongoDB documents related to the XForm.

Notes

• A new column (mongo_uuid) has been added to the XForm model, which will serve as a unique identifier.
  Ownership Transfer: The logic for transferring an XForm's ownership has been updated to ensure that the mongo_uuid is populated if it is currently null.
• All existing MongoDB documents that match the _userform_id will be updated to include the new mongo_uuid value, ensuring consistency across the database.
• The ParsedInstance.to_dict_for_mongo() method has been modified to prioritize the mongo_uuid over _userform_id when exporting data. If mongo_uuid is not null, _userform_id will be set to mongo_uuid; otherwise, the original logic will be maintained.
• The mongo_userform_id property in the OpenRosaDeploymentBackend class has been updated to return the mongo_uuid when available, ensuring that the correct ID is used during operations.

[notion-workspace]

Implement mongo_owner_form_id

[noliveleger]

You can use the XForm object from the deployment, i.e.: self.asset.deployment.xform

[noliveleger]

KeyError? when can this error happen?

[rajpatel24]

Thanks for the review Olivier. The KeyError can occur when the formid key is missing from the backend_response dictionary. This is typically the case in certain test scenarios, such as ConflictingVersionsMockDataExports, where mock data doesn't include the formid key.

When self.xform is accessed, it attempts to retrieve the formid from backend_response, which raises a KeyError if it's not present.

[noliveleger]

Please keep methods sorted alphabetically and let's use KpiUidField.generate_unique_id() which already generates a random string (don't forget to clean imports after).