Support duplicate feedback

**Is your feature request related to a problem? Please describe.**
Currently feedback must be unique of user_id,item_id,feedback_type. In our usecase we would like the model to take in to account the number of times the feedback was provided. eg: If an item was viewed multiple times.

**Describe the solution you'd like**
A clear and concise description of what you want to happen.
Multiple triads of user_id,item_id,feedback_type can be inserted as feedback.

**Describe alternatives you've considered**
A clear and concise description of any alternative solutions or features you've considered.
- Multiple 'sub' feedback types eg 'viewed-1', 'viewed-2'

**Additional context**
Add any other context or screenshots about the feature request here.