Generate Sick Certificates with QR Code for verification

[nishant-nayak]

• For a given appointment, generate a PDF file with the diagnoses associated with that appointment
• Create a new endpoint to verify the legitimacy of the document, which accepts the hash of the document ID as a GET parameter
• Generate a QR code that calls the aforementioned endpoint and verifies the legitimacy of the document

Based on functional requirements documented in the SRS.