Function renderAlternativeParts

apps/sim/tools/gmail/utils.ts:397–413

* Render the inner part of a `multipart/alternative` section (text/plain * followed by text/html, per RFC 2046 — clients pick the last format they * understand).

(plain: string, html: string, boundary: string)

 * understand).
 */
function renderAlternativeParts(plain: string, html: string, boundary: string): string[] {
  return [
    `--${boundary}`,
    'Content-Type: text/plain; charset="UTF-8"',
    'Content-Transfer-Encoding: base64',
    '',
    ...encodeBodyBase64(plain),
    '',
    `--${boundary}`,
    'Content-Type: text/html; charset="UTF-8"',
    'Content-Transfer-Encoding: base64',
    '',
    ...encodeBodyBase64(html),
    '',
    `--${boundary}--`,
  ]
}

/**
 * Build a `multipart/alternative` email (without attachments). Always emits