- Add login function to authenticate with JMAP server
- Add functions to retrieve and query mailboxes
- Add functions to retrieve email messages in mailboxes
- Make all functions follow RFC8621 JMAP Mail spec

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Co-Authored-By: Claude <noreply@anthropic.com>

This commit implements the JMAP Mail extension as specified in RFC8621, including:
- Mailbox, Thread, and Email type definitions
- Email submission and Identity types
- Vacation response handling
- Helper functions for type conversion
- Structure and API patterns matching the core JMAP module

🤖 Generated with [Claude Code](https://claude.ai/code)
Co-Authored-By: Claude <noreply@anthropic.com>

Implemented a comprehensive JMAP API client with the following features:
- HTTP request/response handling using cohttp-lwt-unix
- Session object fetching and parsing
- Core request serialization and response parsing
- Binary blob upload and download functionality
- Proper error handling with detailed error types

The module follows RFC8620 specifications for all API interactions,
including authentication, content handling, and URL template processing.

Note: Implementation currently has a compilation issue with ezjsonm package
that needs to be resolved.

🤖 Generated with [Claude Code](https://claude.ai/code)
Co-Authored-By: Claude <noreply@anthropic.com>

Implements comprehensive OCaml type definitions for the JMAP protocol:
- Basic data types (id, int_t, unsigned_int, date, utc_date)
- Core objects (error, set_error, invocation, result_reference)
- Filter and sorting mechanisms
- Account and session management
- Push notification structures
- Request/response structures
- Standard method argument and response types

All types are documented with corresponding RFC section references.

🤖 Generated with [Claude Code](https://claude.ai/code)
Co-Authored-By: Claude <noreply@anthropic.com>