- Added/Updated headers
- Added script to update copyright headers

- corrected unitary test order and one-by-one execution
- extractedunitary test constant to separate file
- added updated_at refresh for Service and Slice entities
- corrected return types for Connection entity
- prepared PolicyRule entity to raise events and corrected return types of methods

- extended grpc-to-enum tool to support arbitrary enum item names
- added PolicyRuleState enum model
- misc minor comment corrections
- misc import reorderings
- migrated Connection model and methods
- migrated PolicyRule model and methods
- removed unused files