Refactor booking retrieval to return errors instead of nil values,
enabling more robust error handling throughout the booking, payment,
and PDF endpoints. Add custom HTTP error page rendering for not found
and internal server errors. Update interfaces and tests to match new
method signatures. This improves user feedback and code maintainability.
### TL;DR
Enhanced invoice generation with improved formatting and Euro symbol display
### What changed?
- Added Euro symbol (€) to monetary values in the invoice template
- Implemented new invoice data structure with dedicated types for lines and payments
- Created ToInvoice method to properly format booking data for invoice generation
- Added HTML template parsing and rendering functionality
- Improved date formatting for consistency
- Added new API endpoint for booking creation
### How to test?
1. Create a new booking through the API
2. Navigate to the PDF generation endpoint
3. Verify that monetary values display with Euro symbol
4. Check that dates are properly formatted
5. Confirm that payment history and totals are correctly calculated
6. Validate that the generated HTML maintains proper formatting
### Why make this change?
To improve invoice readability and consistency by standardizing monetary value display and providing better data structure for invoice generation. This change also makes the system more maintainable by separating concerns between data transformation and presentation.
* add comments to main file
* create health check handler
health check
* use naming convention for booking handler
* use naming convention for hamndlers
naming convention
* clean up
