Front end can't match groups with records

[seancolsen]

Previously, when grouping records using the REST API, each group object returned had a result_indices field. The front end relied on this field to match groups up with their corresponding result records.

The RPC-based records grouping added in #3721 doesn't seem to provide any way for the front end to match groups to their records.

To minimize implementation time, ideally, we'd use the same structure — a result_indices (array of numbers) within each group object.

I can see that the new RPC API does provide a results_eq, but that doesn't fully allow the front end to match groups with records. For example if I'm grouping an email column by email domain, then results_eq will show only the domain, and the front end won't be able to know what the domain is for the emails within each record.