Several subsystem require capabilities provided by the Undertow subsystem.
Unfortunately, these capabilities are poorly encapsulated, i.e. most of these capabilities are interfacts/classes defined by the Undertow subsystem itself. Worse, many of these capabililities expose the MSC Service interface to consumers (see WFLY-8512). This requires that consumers depend on the Undertow subsystem itself rather than some smaller SPI module.
This module will also make the org.wildfly.clustering.container module redundant (as this only exists because of the lack of such an SPI module).