Mirroring a local flag onto a remote account

The feature is one switch: when I mark a record as followed here, mark it followed on my account too. Almost all the difficulty is in what the switch means at its two edges, and in what the per-item call is allowed to return.

// adapted — the whole contract, in the repository interface
/**
 * Records the flag locally, and mirrors it onto the account when mirroring is enabled.
 *
 * Returns null when mirroring is off or was not attempted, true when the account was updated,
 * false when the call failed — the caller decides whether that is worth telling the user about.
 * The local flag is written either way: marking a record must not depend on the network.
 */
suspend fun setFollowed(recordId: String, followed: Int): Boolean?