Add unit test for classNames module in frontend

[marsbergen]

Context

We use the classNames modules in many components, it should be able to process many forms of json and output a string without duplicates or null values.

Technical Requirements

• Classnames like classNames('italic', 'text-color-red', active && 'font-bold') should output italic text-color-red when not active and italic text-color-red font-bold when the component has an active prop.