[DCP - Ingestion]Adds the provenance URL

[gmechali]

This PR modifies the JSONLD exporter to also add the provenance URL on observation nodes, and then reads back the provenance URL from the MCFGraph, to write it in the Spanner Observation Mutation.

I published a new dataflow test template and successfully loaded the undata import in a test spanner DB.

[codacy-production]

Not up to standards ⛔

🔴 Issues 2 medium · 4 minor

Alerts:
⚠ 6 issues (≤ 0 issues of at least minor severity)

Results:
6 new issues

Category	Results
Security	1 medium
CodeStyle	4 minor
Complexity	1 medium

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🟢 Metrics 0 complexity · 0 duplication

Metric	Results
Complexity	0
Duplication	0

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[gemini-code-assist]

Code Review

This pull request adds provenance URLs to the JSON-LD export by fetching them from the database and including them in the observation graph. Review feedback identifies a significant performance issue where the provenance URL query is executed redundantly for every data chunk, potentially causing full table scans; it is recommended to fetch this data once in the main process. Additionally, the reviewer suggests using expand_id for the URL values and adding a check for empty strings to ensure consistency and data integrity.

[keyurva]

Thanks Gabe!