(SP: 1) Review model validation

## Description
There should be the following validation rules for Review model:
- **comment** must be required and trimmed
- **rating** – must be required, trimmed and have a value in range 1-5
- **author** must be required
- **targetUserId** must be required
- **targetUserRole** must be required
- **offer** must be required

## Acceptance Criteria
- [ ] all of the rules above must be addded