Enable sending multiple `data` fields, each with its own `metadata` if needed

[renan-souza]

            with FlowceptTask(used=used_args) as t:
                repo_root = Path(__file__).resolve().parents[2]
                img_path = repo_root / "docs" / "img" / "flowcept-logo.png"
                with open(img_path, "rb") as fp:
                    img_data = fp.read()

                img_path2 = repo_root / "docs" / "img" / "architecture.pdf"

                t.end(generated={"b": 2}, data=img_data, custom_metadata={
                    "mime_type": "image/png", "file_name": "flowcept-logo.png", "file_extension": "png"}
                      )
                t.send()