SQLToGCSOperators Add Support for Dumping JSON

[patricker]

Description

If your output format for a SQLToGCSOperator is json, then any "dict" type object returned from a database, for example a Postgres JSON column, is not dumped to a string and is kept as a nested JSON object.

Add option to dump dict objects to string in JSON exporter.

Use case/motivation

Currently JSON type columns are hard to ingest into BQ since a JSON field in a source database does not enforce a schema, and we can't reliably generate a RECORD schema for the column.

Related issues

No response

Are you willing to submit a PR?

• Yes I am willing to submit a PR!

Code of Conduct

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[patricker]

Also, somewhat unrelated, the schema generated if a column is of type "JSON" is for a column of type "STRING". If you try to load the data into BigQuery using the generated schema it will fail if you don't dump the dictionaries to string first.