Clarify queueing behaviour for pending Presence messages

[paddybyers]

The spec is ambiguous in respect of this question.

Presence messages are queued in a channel while in the ATTACHING state (and later retried following any suspend). If there is a presence update/enter already queued for a given clientId, and then there is a superseding update for the same clientId - are both supposed to be sent to Ably when the channel completes attachment, or is it acceptable only to send the later update (provided both callbacks get called)?

(Internal discussion: https://ably-real-time.slack.com/archives/CURL4U2FP/p1675263889316679.)

Both approaches appear to be acceptable in the current spec - so either we should state that explicitly, or require one behaviour or the other. FWIW ably-js sends all messages, avly-java discards superseded messages for a given clientId.

[sync-by-unito]

➤ Automation for Jira commented:

The link to the corresponding Jira issue is https://ably.atlassian.net/browse/SDK-3302