MigrationResult interface
What a migration verb answers with.
payload is an opaque document the node wrote and only the node reads: ferry it to the other instance’s matching node, verbatim, and never parse it. Everything the handover needs to know about CMAF playlists — positions, windows, discontinuity counts, fragment anchors, the version the two instances are speaking — lives inside it, in the engine.
refused is the exception, and the only thing a caller reads: a non-empty string means this node declined the verb, and it declined BEFORE doing anything irreversible. Abandon the migration and say why.
Signature:
export interface MigrationResult