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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summary: Allow server administrators to probe any user
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This module lets server administrators send `<presence type="probe"/>`
to any local user and receive their presence in response, bypassing
roster checks.