Add D1 database endpoints support

[EmilLindfors]

Summary

This issue requests the addition of comprehensive D1 database endpoint support to cloudflare-rs. Currently, the library only includes D1 bindings for Workers but lacks the database management endpoints needed for full D1 operations.

Background

D1 is Cloudflare's serverless SQL database service that provides SQLite-compatible databases with global distribution. While cloudflare-rs supports D1 bindings in the Workers module, it's missing the core database management functionality.

Missing Functionality

The following D1 API endpoints are currently not implemented:

Database Management

• GET /accounts/{account_id}/d1/database - List databases
• POST /accounts/{account_id}/d1/database - Create database
• GET /accounts/{account_id}/d1/database/{database_id} - Get database details
• DELETE /accounts/{account_id}/d1/database/{database_id} - Delete database
• PUT /accounts/{account_id}/d1/database/{database_id} - Update database
• PATCH /accounts/{account_id}/d1/database/{database_id} - Partial update database

Data Operations

• POST /accounts/{account_id}/d1/database/{database_id}/query - Execute SQL queries
• POST /accounts/{account_id}/d1/database/{database_id}/raw - Execute raw SQL queries
• POST /accounts/{account_id}/d1/database/{database_id}/export - Export database
• POST /accounts/{account_id}/d1/database/{database_id}/import - Import database

Proposed Solution

Implement a complete d1 endpoints module that provides:

1. Database Management: Full CRUD operations for D1 databases
2. Query Execution: Both parameterized and raw SQL query support
3. Data Import/Export: Database backup and restore capabilities
4. Configuration Management: Read replication and location hint support
5. Comprehensive Testing: Full test coverage for all endpoints
6. API Specification Compliance: 100% compliance with official OpenAPI spec

Implementation Details

• Follow existing cloudflare-rs patterns and conventions
• Use official Cloudflare OpenAPI specification as source of truth
• Implement proper error handling and response types
• Include comprehensive documentation and examples
• Maintain both blocking and async API support

Impact

This would fill a significant gap in cloudflare-rs functionality and enable developers to:

• Manage D1 databases programmatically from Rust applications
• Execute SQL queries and manage database schemas
• Implement automated backup/restore workflows
• Build complete database-driven applications on Cloudflare's platform

References

• Cloudflare D1 Documentation
• Cloudflare API Documentation
• D1 REST API Reference

I have a complete implementation ready that follows all project conventions and passes comprehensive tests. I would be happy to submit a PR if this feature addition is welcomed.