Use token_hex from secrets instead of choice

CURA-8401

cura/OAuth2/AuthorizationHelpers.py

@@ -139,11 +139,11 @@ class AuthorizationHelpers:
     def generateVerificationCode(code_length: int = 32) -> str:
         """Generate a verification code of arbitrary length.
 
-        :param code_length:: How long should the code be? This should never be lower than 16, but it's probably
+        :param code_length:: How long should the code be in bytes? This should never be lower than 16, but it's probably
         better to leave it at 32
         """
 
-        return "".join(secrets.choice("0123456789ABCDEF") for i in range(code_length))
+        return secrets.token_hex(code_length)
 
     @staticmethod
     def generateVerificationCodeChallenge(verification_code: str) -> str: