PlaceholderParsedSection constructor

Represents a parsed section of a placeholder string, typically extracted from a raw placeholder like #{key:default}.

This class holds:

• The key part (e.g., key)
• The fallback part if present (e.g., default)

It is used during placeholder parsing to distinguish between the key to be resolved and the fallback value to use when resolution fails.

Example:

#{app.name:MyApp}

would be parsed into:

ParsedSection('app.name', 'MyApp');

This class is used internally during placeholder analysis and decomposition, and is not meant to be exposed to end users directly.