[FEATURE]: Allow Multiple Categories

[jamesqquick]

Is your feature request related to a problem? Please describe.
As a user uploading a deal, I would llike to be able to choose multiple categories for my deal

Describe the solution you'd like

• database updates to add table for categories, and DealCategory table to handle many to many relationship
• form should be updated to include checkboxes to select multiple categories

Describe the benefits of your solution
This allows more visibility for deals that are not exclusively tied to one category

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