Toolchain identification information, which will be matched against project requirements.
            <p>For Maven 2.0.9 to 3.2.3, the actual content structure was completely open: each toolchain type would
            define its own format and semantics. This was generally a properties format.
            <p>Since Maven 3.2.4, the type for this field has been changed to Properties to match the de-facto
            format.