This protocol is used to build JoinGroup requests.

V0 Options

• group_id (required): The consumer group ID
• session_timeout (required): Session timeout in milliseconds
• member_id (required): The member ID (empty string for new members)
• group_protocols or topics (required): Group protocols or topics list
• protocol_type (optional): Protocol type, defaults to "consumer"

V1-V4 Options (adds to V0)

• rebalance_timeout (required): Rebalance timeout in milliseconds

V5-V6 Options (adds to V1-V4)

• group_instance_id (optional): Static membership instance ID (nil for dynamic)

All known versions (V0-V6) have explicit implementations. The Any fallback handles unknown future versions.