Model fields - datatype and validation checks

## Basic Information
The `price` field in the model should be a number, also make sure the requests are being validated (e.g. email/mobile is valid using regex, status is from the list of allowed statuses etc)

And make sure pages that reference the model handles the change correctly

Start by locating the model, request-handling entry points, and pages that reference it. Inspect the existing price, email, mobile, and status handling before determining the required validation behavior; done means the model fields and requests reject invalid values and all referencing pages still work correctly.

Written by the indexing model from the issue text.