Add EPC QR code to make bank transactions easier (#61)

See https://de.wikipedia.org/wiki/EPC-QR-Code#EPC-QR-Code_f%C3%BCr_%C3%9Cberweisung_erstellen for more information about the EPC coding

Co-authored-by: dusker <dusker@gmx.de>
Reviewed-on: #61
Co-authored-by: dusker <jens.graef+ezgg@posteo.de>
Co-committed-by: dusker <jens.graef+ezgg@posteo.de>

src/ezgg_lan_manager/services/AccountingService.py

@@ -1,4 +1,6 @@
+import io
 import logging
+import qrcode
 from collections.abc import Callable
 from datetime import datetime
 from decimal import Decimal, ROUND_DOWN
@@ -74,3 +76,29 @@ class AccountingService:
             return "0.00 €"
         rounded_decimal = str(euros.quantize(Decimal(".01"), rounding=ROUND_DOWN))
         return f"{rounded_decimal} €"
+
+    @staticmethod
+    def make_payment_qr_image(beneficiary_name, beneficiary_bic, beneficiary_iban, text, amount_euros=None) -> bytes:
+        text = text.replace("\n",";")
+        amount_formatted = "EUR{:.2f}".format(amount_euros) if amount_euros else ""
+        epc_text = f"""BCD
+002
+1
+SCT
+{beneficiary_bic}
+{beneficiary_name}
+{beneficiary_iban}
+{amount_formatted}
+
+
+{text}
+"""
+        qr = qrcode.QRCode(
+            version=6,
+            error_correction=qrcode.constants.ERROR_CORRECT_M,
+        )
+        qr.add_data(epc_text)
+        img = qr.make_image()
+        img_bytes = io.BytesIO()
+        img.save(img_bytes)
+        return img_bytes.getvalue()