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Header key for storing the tail context name.

Header key for storing the tail function name.

Prefix for all waiting chain tail header keys.

Header key for storing the tail processor name.

Header key for storing the tail stage.

Extracts a waiting chain tail from the message header.

Converts a CommandStage to a WaitingChainTail with optional function criteria. For stages that require function waiting, the provided function is used. For stages that don't require function waiting, an empty function is used.