getContentType abstract method
Extracts the content type from a raw content map.
Retrieves the message type identifier (e.g., "01" for text, "88" for command) from a raw content map with a fallback default value if the type field is missing.
@param content - Raw content map containing type metadata
@param defaultValue - Fallback value if type is not found
@return Extracted content type (or defaultValue if not present)
Implementation
String? getContentType(Mapping content, [String? defaultValue]);