Refactoring augmentation-lambda persistence id assignment (#610)

## Description

This PR is intended to try to clean up and streamline _process_record so
that the logic for when and how we fall back to original EICR cleaner. I
personally find the currently written process a bit tough to follow and
am hoping this will help clarify.

## Related Issues

## Additional Notes

[Add any additional context or notes that reviewers should know about.]

<--------------------- REMOVE THE LINES BELOW BEFORE MERGING
--------------------->

## Checklist

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well-documented.
- [ ] I have updated the documentation, if applicable.
- [ ] I have added or updated test cases to cover my changes, if
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## Checklist for Reviewers

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Author: robertandremitchell

e2e/snapshots/test_e2e/test_upload_and_process/augmentation_metadata.json

@@ -1,8 +1,8 @@
 {
-  "augmented_eicr_id": "1.2.840.113619.21.1.139060385287897942.5.3",
+  "augmented_eicr_id": "1.2.840.113619.21.1.139060385287897942.5.3^1899729054011780",
   "error": "Unable to find tag in eICR document for XPath: /ClinicalDocument/setId",
   "nonstandard_codes": [],
-  "original_eicr_id": "1.2.840.113619.21.1.139060385287897942.5.3",
+  "original_eicr_id": "1.2.840.113619.21.1.139060385287897942.5.3^1899729054011780",
   "passthrough": true,
   "passthrough_reason": "augmentation_exception"
 }

e2e/snapshots/test_e2e/test_upload_and_process/augmented_eicr.xml

@@ -1,8 +1,8 @@
 {
-  "augmented_eicr_id": "2025/09/03/1-5f84c7a5-91d7f5c6a2b7c9e08f0d1234",
+  "augmented_eicr_id": "1.2.840.114350.1.13.370.2.7.8.688883.608381234",
   "error": null,
   "nonstandard_codes": [],
-  "original_eicr_id": "2025/09/03/1-5f84c7a5-91d7f5c6a2b7c9e08f0d1234",
+  "original_eicr_id": "1.2.840.114350.1.13.370.2.7.8.688883.608381234",
   "passthrough": true,
   "passthrough_reason": "no_relevant_schematron_errors"
 }