RequiredCapabilityListener is a listener interface that may be implemented by a Carbon component developer. When
all the required capabilities are available, this event is asynchronously delivered to a RequiredCapabilityListener.
A RequiredCapabilityListener must be registered as an OSGi service. A bundle which registers an implementation
of this interface should contain a corresponding Provide-Capability manifest header.
e.g Provide-Capability: osgi.service;effective:=active;
objectClass="org.wso2.carbon.startupresolver.RequireCapabilityListener";
capability-name="org.wso2.carbon.sample.transport.mgt.Transport"
This OSGi service must also be registered with a service property called "required-service-interface" as shown
in the above example. The value of this service property must be the key or the interface of the required OSGi
service.