PartitionById arranges the elements of a slice into any number of partitions, where each partition contains elements grouped by a common ID.

Rule data formatted as a single YAML document containing yaml-encoded []rulefmt.RuleGroup keyed by tenant ID: <tenantID>: - name: ..

Rule data formatted as JSON containing the prometheus response metadata and a list of rule groups, each of which has a field "file" containing the tenant ID: {"status":"success","data":{"groups":["file":"<tenantID>", ...]}}.