Support __text/__value custom display query variables

[njvrzm]

Is your feature request related to a problem? Please describe.
Users migrating from the PostgreSQL datasource to the redshift datasource lose the ability to create query variables with custom display values using __value and __text columns as described in the documentation.

See this community thread for an example.

Describe the solution you'd like
Redshift should support this feature to ease migration.

[StephenKing]

Thanks @njvrzm for filing the issue in my name.

If someone can give me a pointer, how this functionality can be added, I can try to file a PR.

Without this, dashboards variables are significantly less comfortable (users now have to enter the customer ID to filter for, instead of previously the ability to select based on the name of the customer) from a query variable.

[sarahzinger]

relates to grafana/athena-datasource#286

[StephenKing]

Indeed, using text and value instead of __text and __value works.

[sarahzinger]

Just a heads up this is still broken, see discussion here: grafana/athena-datasource#286

[idastambuk]

The use of text and value variables was misleading in the Grafana docs. We have updated the Redshift docs recently - tldr this is supported with text and value variables instead of __text and __value.