OF-3176: Fix stanza loss during outgoing S2S session teardown

[guusdk]

When an outgoing server-to-server (S2S) connection closes, the connection is marked closed immediately, but route removal from the routing table happens asynchronously during teardown. This creates a short race window where routing can still send stanzas to a closing session, which then sees a closed connection and drops the stanza.

This change fixes that behavior by waiting for teardown to fully complete before re-routing a stanza that reached a closed outgoing session. Waiting for close completion ensures stale route cleanup has finished, after which normal routing can use an existing replacement session or create a new one.

A new system property, xmpp.server.session.redelivery-timeout (default: 30 seconds), controls how long Openfire waits for teardown completion before returning an error to the sender.

[Copilot]

Pull request overview

This PR addresses OF-3176 by preventing stanza loss when an outgoing S2S session is closing: instead of immediately bouncing/dropping on a closed connection while route removal is still in-flight, it waits for teardown completion and then re-routes the stanza (with a configurable timeout).

Changes:

• Add a new dynamic system property (xmpp.server.session.redelivery-timeout, default 30s) to bound how long to wait for outgoing-session teardown completion before abandoning re-delivery.
• Update outgoing S2S stanza delivery logic to await Connection#getCloseFuture() completion before re-routing stanzas that hit a closed connection, while avoiding “double-bounce” for error stanzas.
• Add i18n strings (EN + NL) for the new system property description.

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 4 comments.

File	Description
xmppserver/src/main/java/org/jivesoftware/openfire/session/LocalOutgoingServerSession.java	Adds the redelivery-timeout property and re-delivery logic that waits for teardown completion before re-routing.
i18n/src/main/resources/openfire_i18n.properties	Adds English description for the new system property.
i18n/src/main/resources/openfire_i18n_nl.properties	Adds Dutch description for the new system property.

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