correct dataset template field name

[marengaz]

fixes

jsonPayload.message="Cache Exception, will retry after 10 seconds: com.google.cloud.bigquery.BigQueryException: Invalid dataset ID \"ben_{_metadata_dataset}_log\". Dataset IDs must be alphanumeric (plus underscores and dashes) and must be at most 1024 characters long."

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[pabloem]

fyi @dhercher

[bvolpato]

Hi @marengaz -- thanks for your contribution here.

Unfortunately we ran behind on reviews / merge, and the structure of the project changed a bit. Is there still interest in pursuing this change?

We can work together on a plan to resolve conflicts + review the code.