startConversation
open suspend fun startConversation(remoteId: String, initialMessage: SanitizedText? = null, accountId: String? = null): SendResult
Starts a new conversation with remoteId, optionally sending initialMessage.
accountId picks which locally-connected account originates the conversation when a protocol has more than one account connected simultaneously (e.g. two XMPP or Matrix accounts logged in at once). When null, implementations fall back to a single-account default, which may be ambiguous if several accounts of the same protocol are connected.