These functions are used to prepare text-based documents (plain text,
Markdown, CSV, HTML, code files, and, for providers that support them,
Word/Excel files) as input to the chatbot. content_document_url() is
used to provide a URL to a document, while content_document_file() is
used for local files.
Not all providers support all document types, so check the documentation
for the provider you are using. For PDFs, use content_pdf_file() or
content_pdf_url() instead.
Both functions embed the document's contents in every request, so for a
large document, or one you'll refer to across several turns, prefer
chat$file_upload(). It uploads the file once and later turns reference
it by id.