Feature/add suppliers

[proffalken]

This PR adds suppliers to the API, allowing you to assign multiple components to multiple suppliers to ensure you are getting the best value for money when purchasing things.

It also provides fields for "marking up" products, and returns the total price that the user will pay along with the difference between the cost from the supplier and the price charged so purchasers can see how much they are contributing to the space with each purchase.

[sonarqubecloud[bot]]

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