Use Google auth proxy to connect to Cloud SQL

[bendnorman]

we're currently white-listing IP addresses of our local machine and the github runners to interact withe the production database. We should really be using cloud auth proxy to authenticate.

Before taking this on we should decide if we want to migrate to BigQuery because its cheaper.

Tasks

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1. Setup cloud auth proxy locally. We could maybe use docker for this
2. Setup cloud auth proxy in the github action
3. Add connection details to Secret Manager
4. Update the documentation