[FEAT]: Attach documents to messages

[blaineatnoeonai]

What would you like to see?

Currently, only administrators and managers can upload documents, and then those documents must be added to a workspace and accessed through RAG / pinning.

It would be good if users could upload attachments to messages. Attachments would be processed / OCRed and added to the context of the current conversation, but not added to the RAG system / made available to other users. This is a very common usage pattern, supported by ChatGPT, Claude, etc.