Create metrics endpoints for general TMF-related information
Create endpoints:
- GET /tmf-api/metrics/registeredIndividuals
- Exp. Resp: {registeredIndividuals: 23}
- GET /tmf-api/metrics/publishedServiceSpecifications
- Exp. Resp: {publishedServiceSpecifications: 13} - TIP: get all ServiceCategories and count the allocated serviceCandidates
- GET /tmf-api/metrics/registeredResourceSpecifications
- Exp. Resp: {registeredResourceSpecifications: 15}