mod_cloud_notify_encrypted: Ensure body substring remains valid UTF-8 The `body:sub()` call risks splitting the string in the middle of a multi-byte UTF-8 sequence. This should have been caught by util.stanza validation, but that would have caused some havoc, at the very least causing the notification to not be sent. There have been no reports of this happening. Likely because this module isn't widely deployed among users with languages that use many longer UTF-8 sequences. The util.encodings.utf8.valid() function is O(n) where only the last sequence really needs to be checked, but it's in C and expected to be fast.

Contributing
============

Guidelines for developers
-------------------------

-   Each module should be contained in a folder of its name (e.g.\
     `mod_ping/mod_ping.lua`)
-   Each module should have a `README.markdown` page in their folder
    with a description, usage, configuration and todo sections (feel
    free to copy an existing one as a template)
-   Commit messages should begin with the name of the plugin they are
    for (e.g. `mod_ping: Set correct namespace on pongs`)

Instructions on cloning the repository are at
<https://prosody.im/doc/installing_modules#prosody-modules>