server: allow customizing BigQuery endpoint

[hgiasac]

Is your proposal related to a problem?

There is some BigQuery emulator library, e.g https://github.com/goccy/bigquery-emulator. The client can connect with the emulator with a custom endpoint, e.g http://0.0.0.0:9050. It's useful for local development and testing.

Describe the solution you'd like

Add an env variable named HASURA_GRAPHQL_BIGQUERY_SERVICE_ENDPOINT. The default value is https://bigquery.googleapis.com. This variable is global that takes effect on all BigQuery data sources.

graphql-engine/server/src-lib/Hasura/Backends/BigQuery/Execute.hs

Line 240 in 54546fc

bigQueryProjectUrl projectId =

Describe alternatives you've considered

We can allow this setting to individual data sources. It's more flexible but IMO it isn't necessary. Moreover it also takes more efforts for the console team

If the feature is approved, would you be willing to submit a PR?

Yes, if I have time to do it.