Dev: Add BIT user attributes to MS User db model | BIT-MS Integration

## Description
As a contributor,
I need to add BIT UserExtensionModel attributes to MS UserModel,
so that I can integrate BIT and MS user schemas into one for BIT-MS full integration.

## Acceptance Criteria
### Update [Required]
- [ ] Add Timezone, is_organization_rep field as they are
- [ ] Add user's additional_info as JsonCustomType instead of JSONB (open for discussion if this field is needed or not)
- [ ] changes to be merged to `bit` branch, not `develop`

## Definition of Done
- [ ] All of the required items are completed.
- [ ] Approval by 1 mentor.

## Estimation
1 day