Cédric Luthi de847b90e4 Improve conversion error messages
When a conversion to an enum fails, list all the valid enum values in the error message.

Message before this commit:
> Error: heimday is not a valid value for DayOfWeek.

Message after this commit:
> Error: Failed to convert 'heimday' to DayOfWeek. Valid values are 'Sunday', 'Monday', 'Tuesday', 'Wednesday', 'Thursday', 'Friday', 'Saturday'
2023-01-24 19:40:11 +01:00
..
2021-12-23 16:50:31 +01:00
2022-11-10 12:01:13 +01:00