OSGi uses a generic Provide-Capability/Require-Capability model that
allows to declare requirements beyond the classic Import-Package and
Require-Bunlde. A common example is a bundle that provides a DS
component and needs an extender to actually construct the component and
inject the services. Another is a logging API that needs a provider.

These are especially needed because in such scenario a provider/consumer
do not know each other and should not depend directly (only loosely
coupled). Currently such providers are still pulled in even though they
are not contribute to the compilation classpath as they are completely
invisible at runtime - there is a wiring but no classloader access
granted.

This now only follows build time requirements to avoid the situation.