Implement ParticipantService

[paullatzelsperger]

implement a ParticipantService, that perform CRUD operations, regenerates keys and emits events:

public interface ParticipantService {
  Result<Void> createParticipantContext(ParticipantContext context);
  Result<Void> [get|delete]ParticipantContext(String participantId);
  Result<String> regenerateApiToken(String participantId);
}

As a minimum, the ParticipantContext should contain the following information:

public class ParticipantContext {
	String participantId;
	String createdDate;
	String lastModifiedDate;
	int state; // CREATED, ACTIVATED, DEACTIVATED
	String apiToken; // or apiTokenAlias
}