Enable custom branding for outbound document emails

Customers frequently send important documents like invoices and purchase orders to their own clients directly from our platform. They need these communications to consistently reflect their company's unique brand identity, rather than Coreloops' default branding. To address this, we aim to empower users to customize the branding on outbound email templates. This will enable the use of their own company logo in the email header, ensuring a seamless and professional brand experience for their recipients.