Add from_str and as_decimal

[1.3.0] - 2022-12-01

Added

• Add a property for PublicationStatus: as_decimal to get a int value in decimal.
• Add a property for ChoiceEnum: as_decimal to get a int value in decimal.
• Add a classmethod for PublicationStatus: from_str to get a element of Enum corresponding to a string.
• Add a classmethod for ChoiceEnum: from_str to get a element of Enum corresponding to a string.