Add RichText Editor to Email Workflow Node

[FelixMalfait]

Overview

Replace the current plain text body field in Twenty's workflow send email action with a rich text editor leveraging the existing BlockEditor infrastructure. The solution must maintain backward compatibility with existing email workflows while enabling rich formatting capabilities including bold, italic, links, lists, and standard email formatting options.

Context

• Existing System State: Send email workflow node uses FormTextFieldInput with multiline for body content, stored as plain string in workflow settings, sanitized with DOMPurify before sending
• Gap Being Addressed: Users cannot create rich formatted emails within workflows, limiting professional email communication capabilities
• Available Infrastructure: Twenty has comprehensive BlockEditor system with BlockNote, FormRichTextV2FieldInput pattern, and rich text persistence mechanisms already implemented

Requirements

• Replace the plain text body field with a rich text editor component
• Preserve workflow variable picker integration
• Migrate existing workflow configurations
• Store rich text content in a format compatible with editing but send it in a format compatible with email rendering

We're talking about the body field here:

[StephanieJoly4]

@FelixMalfait , we (Raphaël) found the similar issue I was talking about - in case this helps
twentyhq/core-team-issues#1319