This change integrates service level functionality into the CQL authentication and connection handling:
- Add scheduling_group_name to client_data to track service level assignments
- Extend SASL challenge interface to expose authenticated username
- Modify connection processing to support tenant switching:
- Add switch_tenant() method to handle scheduling group changes
- Add process_until_tenant_switch() to handle request processing boundaries
- Implement no_tenant() default executor
- Add execute_under_tenant_type for scheduling group management
- Update connection lifecycle to properly handle service level changes:
- Initialize connections with default scheduling group
- Support dynamic scheduling group updates when service levels change
- Ensure proper cleanup of scheduling group assignments
The changes enable proper scheduling group assignment and management based on
authenticated users' service levels, while maintaining backward compatibility
for connections without service level assignments.
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