Custom email templates

[fusion94]

Summary

Allow agreement owners to customize the notification email body and subject line sent when contributors sign.

Motivation

Organizations want branded, personalized email notifications that match their communication style rather than generic CLAHub emails.

Implementation notes

• Per-agreement email template with Handlebars/Mustache variables (contributor name, repo, agreement title, etc.)
• Template editor in agreement settings with live preview
• Default template as fallback
• Subject line customization
• Consider: separate templates for different events (signature, revocation, version bump)

Phase

Phase 6: Integrations (v3.0 roadmap)