Change product quantity to be a string

[LightJack05]

• apparently a quantity can be a string and therefore should be deserialized as such

[Copilot]

Pull request overview

Updates the Product data model to treat product_quantity as a string instead of a number, based on upstream data sometimes representing quantity as text.

Changes:

• Changed Product.ProductQuantity type from float64 to string for JSON/BSON decoding.

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[Copilot]

Changing ProductQuantity from float64 to string will likely break BSON decoding from MongoDB when existing documents store product_quantity as a numeric type (and vice versa if some docs store it as a string). The Go MongoDB driver cannot decode a BSON double/int directly into a Go string, so FindOne().Decode()/cursor.All() can start failing at runtime for mixed-type data. Consider introducing a dedicated type for this field that implements BSON unmarshalling (and JSON unmarshalling if needed) to accept both string and numeric representations and normalize to a string, rather than switching the struct field to plain string.

[Copilot]

bson:"product_quantity,truncate" was previously meaningful for a numeric type; on a string field it’s inconsistent with the rest of this struct (no other string fields use truncate) and can be misleading. Recommend dropping the truncate option if the field remains non-numeric, or keeping the field numeric internally and converting at the API boundary.

Suggested change

	ProductQuantity string `json:"product_quantity" bson:"product_quantity,truncate"`
	ProductQuantity string `json:"product_quantity" bson:"product_quantity"`