Required secrets for postgresql in keyvault

Workflow ingestion service needs to connect to the postgresql database (that is primarily used by airflow). This is required in order to implement the feature where we have to query the postgresql dataset.

As of now, there's no clear way to obtain the hostname and username (for db) that will allow us to connect to the postgreql for running the custom queries.

These changes are added as part of the following MR in workflow ingestion service -

osdu/platform/data-flow/ingestion/ingestion-workflow!199 (merged)

The corresponding MR (in infra azure provisioning) that adds these changes is - !549 (merged)

cc: @kibattul