[CUST-5735] feat(messages): add send_raw_mime for raw MIME message send

[benjaminwhtan]

Summary

The v3 API supports sending a raw RFC 822 MIME message (POST /v3/grants/{grant_id}/messages/send?type=mime), but the Python SDK had no way to call it. Customers who need exact control over the outgoing message, such as setting Importance: High / X-Priority: 1 on Microsoft grants, had to hand-roll HTTP requests. This adds messages.send_raw_mime().

client.messages.send_raw_mime(
    identifier=grant_id,
    request_body={"mime": mime_bytes},
)

Changes

• Add Messages.send_raw_mime(identifier, request_body, overrides=None), returning Response[Message]. It follows the repo's request_body TypedDict convention and is named to pair with the existing read-side fields="raw_mime".
• Add the SendRawMimeRequest model. mime accepts str or bytes. Bytes are sent exactly as given; strings are encoded as UTF-8.
• Add _build_raw_mime_form_request, which sends the MIME as a message/rfc822 file part named mime. v3-send's constructMimeReader reads the file part first and streams it to disk. A plain form value only works through a fallback that logs an error, and Go's multipart parser holds plain values in memory with a size cap.
• type=mime is set internally and isn't exposed as a query param, because it selects the endpoint rather than being an option.
• Add unit tests for the resource method (str, bytes, overrides) and the form builder (file part, byte preservation).
• Add the examples/raw_mime_send_demo example and README, and a CHANGELOG entry.

Testing

• Full unit suite passes (491 tests, e2e excluded)
• No new pylint warnings in touched files
• Checked the outgoing request with only the network call mocked: ?type=mime, a multipart/form-data body with a single mime file part, and bytes unchanged
• Live send from a Microsoft grant, using the example script against this branch (editable install). The send succeeded, and the received message in Outlook showed the high-importance flag, with Importance: High and X-Priority: 1 in the message source.

Related

• CUST-5735 (Node and Ruby SDKs still to follow)

🤖 Generated with Claude Code

[pengfeiye]

this is a new feature you might need to update the sdk referrence doc AI should be able to resolve the error on the PR