Distribute UMAPI calls among multiple clients optionally

[kwin]

Due to the strict throttling IMS syncs are really slow. In order to improve the situation the OSGi configuration should optionally support multiple clients (with dedicated client ids/secrets) in order to distribute requests among the clients. Further information in https://adobe-apiplatform.github.io/umapi-documentation/en/api/group.html#throttle and https://adobe-apiplatform.github.io/umapi-documentation/en/api/ActionsRef.html#actionThrottle