Slack adapter: expose the installation a delivery was resolved through to handlers #1058

Package: @chat-adapter/slack@4.41.1

Problem

With an installationProvider, the adapter resolves an installation for each delivery (from authorizations[0].team_id / team_id, or the enterprise id for org-wide installs) and keeps it, with its bot token, in the adapter's own per-delivery store: the protected readonly requestContext: AsyncLocalStorage<{ token, installationId, teamId, enterpriseId, isEnterpriseInstall, botUserId, ... }> field on SlackAdapter. Handlers (onNewMention, onSubscribedMessage, onAction, ...) cannot read it.

A multi-workspace app usually needs exactly that inside a handler: which installation (tenant) this message came through, and that installation's bot token for its own Slack Web API calls. The alternatives available to handlers are wrong or costly:

• message.raw.team is the sender's team. In a Slack Connect channel it is another company's workspace, not the one the app is installed in.
• Looking the installation up again by team id means another getInstallation round trip per message, and still needs the right team id first.

Ask: a public way for a handler to get the current delivery's installation (id and bot token), for example a getter on the adapter.

Related: #874 (the suggestedPrompts resolver missing teamId on one path), the same gap in a different place.

Workaround today

Subclass SlackAdapter and add a public getter over that field (this.requestContext.getStore()), then reach the adapter through thread.adapter in handlers. It depends on a protected field and its shape, so a test has to guard it against adapter upgrades.