mod_rest: Catch and log errors in callback promise chain From the code it looks like it should be possible to reply to an error stanza, but it did not. Turns out I was saved by my local developer mode module which throws errors if an attempt is made to create an errror reply to an error stanza. However nothing collects this error from the promise, so all I got was confusion.

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labels:
summary: Workaround for servers doing EXTERNAL without proper stream headers
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Introduction
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This module is a workaround for servers that try to do s2s
authentication with certificates and SASL EXTERNAL, but do not send
correct stream headers. Notably Openfire versions since 3.7 or 3.8.