mod_rest/rest.sh: Update to use httpie-oauth2 plugin This bash implementation of OAuth2/OIDC was growing to the point where it needed a massive refactor, which made me look into alternatives where I finally settled on implementing oauth2 in a plugin for HTTPie.

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summary: Remote Roster Management
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Introduction
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This module adds support for [XEP-0321: Remote Roster Management] which
is commonly used to allow components such as transports to modify the
rosters of local users.