Parent class for all views extensions.
All classes that inherit from that class must define a constant named
EXTENSION_ID that is unique for each extension type, and is used when
retrieving an extension from a view.
When choosing the identifier to use with your class, you must look at other
defined identifiers to avoid collision. In addition, some ranges are reserved
for specific usage:
- 0x0 to 0xFFFF: reserved for IOLink
- 0x10000 to 0xFFFFFFFF: reserved for external modules by the IOLink team
- Other values: user defined extensions
See also: View::extension