This is more heavily used in Message::send as a way of discerning "real" server errors
from those that are caused by user input. The name itself might not be super fitting either
* Moving code for inserting textual messages into its own function
This splits up the logic a bit for Message::send but this segment of logic is also
much simpler than that of file upload
* Flattening Message::send overall
Keeping this function as flat as can be is crucial as it is one of the heavier+most
important funcs in the whole JSON API codebase
Files are now also generated correctly and asynchronously
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