`Product` catalogue/client-initiated quote request and invoices in Client Portal

What environment are you running? Self Hosted Have you searched existing issues and requests? • I have searched existing issues and requests. Screenshots _No response_ Additional context Would be excellent if clients could self-service in the Client Portal by selecting products made available to them to then be able to request a quote, and/or generate and pay an invoice if it's toggled for that and is in stock (though back-orders would also be ever so cool). Some things would be defined visible prices, other things would be POA without any kind of concrete price ("how long is a piece of string?"). I understand this could be done via the API, but centralizing it all in the Client Portal is such a no-brainer to me as the UX is very nice and users would already be managing invoices and quotes there anyway, and the products already exist in Invoice Ninja. :- ) "Pre-payments" as a concept is already a good step in this direction conceptually, likewis…