////////////// Summary //////////////

Add native macOS calendar integration using real Proton account authentication, not public/shared calendar links. If possible also add editing rights.

////////////// Description //////////////

Currently, adding Proton calendars to macOS requires using public calendar links. This approach has significant limitations and does not meet the expectations for a secure, professional, or privacy-focused calendar integration.
Public links:
- Expose calendar data via static URLs
- Cannot reflect user permissions properly
- Are unsuitable for private, work, or shared calendars
- Do not align with Proton’s security and privacy model

////////////// Problem / UX & Security Issues //////////////

• Public links are a workaround, not a real integration
• No proper authentication or access control
• Difficult to manage multiple calendars and accounts
• Poor experience for professional and enterprise users
• Inconsistent with how Proton Mail accounts work on macOS

////////////// Proposed Solution //////////////

Provide native, account-based calendar integration for macOS that:
- Uses Proton account login (authentication, not public URLs)
- Supports multiple calendars per account
- Respects calendar permissions and sharing rules
- Syncs securely with the macOS Calendar app
- Updates in real time (or near real time)
- Allows easy enable/disable per calendar

////////////// Expected Behavior //////////////

• User signs in with their Proton account
• Calendars appear automatically in macOS Calendar
• Shared calendars work according to permissions
• No public links required at any point

////////////// User Value //////////////

• Proper security and privacy
• Seamless macOS experience
• Better usability for work and personal scheduling
• Makes Proton Calendar viable as a primary calendar on macOS

////////////// Priority Justification //////////////

Calendar access is a core daily workflow. Relying on public links undermines trust, usability, and professional adoption. Account-based integration is essential for serious macOS users.