Adds a new postgreSQL.logicalReplication configuration to allow MSP to generate prerequisite setup for integration with Datastream: https://cloud.google.com/datastream/docs/sources-postgresql. Integration with Datastream allows the Data Analytics team to self-serve data enrichment needs for the Telemetry V2 pipeline.

Enabling this feature entails downtime (Cloud SQL instance restart), so enabling the logical replication feature at the Cloud SQL level (cloudsql.logical_decoding) is gated behind postgreSQL.logicalReplication: {}.

Setting up the required stuff in Postgres is a bit complicated, requiring 3 Postgres provider instances:

1. The default admin one, authenticated with our admin user
2. New: a workload identity provider, using Add support for GCP IAM impersonation cyrilgdn/terraform-provider-postgresql#448 / postgresql: use cyrilgdn/terraform-provider-postgresql#448 managed-services-platform-cdktf#11. This is required for creating a publication on selected tables, which requires being owner of said table. Because tables are created by application using e.g. auto-migrate, the workload identity is always the table owner, so we need to impersonate the IAM user
3. New: a "replication user" which is created with the replication permission. Replication seems to not be a propagated permission so we need a role/user that has replication enabled.

A bit more context scattered here and there in the docstrings.

Beyond the Postgres configuration we also introduce some additional resources to enable easy Datastream configuration:

1. Datastream Private Connection, which peers to the service private network
2. Cloud SQL Proxy VM, which only allows connections to :5432 from the range specified in 1, allowing a connection to the Cloud SQL instance
3. Datastream Connection Profile attached to 1

From there, data team can click-ops or manage the Datastream Stream and BigQuery destination on their own.

Closes CORE-165
Closes CORE-212

Sample config:

  resources:
    postgreSQL:
      databases:
        - "primary"
      logicalReplication:
        publications:
          - name: testing
            database: primary
            tables:
              - users

Test plan

https://github.com/sourcegraph/managed-services/pull/1569

Changelog

• MSP services can now configure postgreSQL.logicalReplication to enable Data Analytics team to replicate selected database tables into BigQuery.