Feature request: Send remote attachment

[humanagent]

https://docs.xmtp.org/inboxes/content-types/attachments
Can make this work given an existing URL

  async sendRemoteAttachment(url: string) {
    try {
      // Fetch the image data
      const response = await fetch(url);
      if (!response.ok) {
        throw new Error(`Failed to fetch the image: ${response.statusText}`);
      }
      const arrayBuffer = await response.arrayBuffer();

      // Create the attachment object
      const attachment = {
        filename: url.split("/").pop() || "image.jpg",
        mimeType: response.headers.get("content-type") || "image/jpeg",
        data: new Uint8Array(arrayBuffer),
      };

      // Encode and encrypt the attachment
      const encryptedEncoded = await RemoteAttachmentCodec.encodeEncrypted(
        attachment,
        new AttachmentCodec(),
      );

      // Create the remote attachment object
      const remoteAttachment: RemoteAttachment = {
        url: url, // Original URL
        contentDigest: encryptedEncoded.digest,
        salt: encryptedEncoded.salt,
        nonce: encryptedEncoded.nonce,
        secret: encryptedEncoded.secret,
        scheme: "https://",
        contentLength: attachment.data.byteLength,
        filename: attachment.filename,
      };

      // Send the remote attachment
      await this.send(remoteAttachment, ContentTypeRemoteAttachment);

      return remoteAttachment;
    } catch (error) {
      console.error("Failed to send remote attachment:", error);
      throw error;
    }
  }