Add ability to cherry-pick products that are visible in the Customer Portal

[crnkovic]

It would be great if we could either globally hide certain products from the Customer Portal, so that customer doesn't see them when they press "Change plan", or even better would be if we could specify the product_ids in POST /v1/customer-sessions and only show these products in the Change Plan slide-over panel.

Use case: creating specific plans for specific customers, e.g. Enterprise.

[pieterbeulque]

Yes, I agree. Slightly related: #8015

[bassemkaroui]

I think this is the easiest proposal to implement that I've yet read in all the discussions around this topic.

[pieterbeulque]

Copying from #5327:

A very basic version of this is now shipped, and you can manage the visibility of a product in places like the Customer Portal through Product Configuration → Visibility. We have more changes coming to the product form soon, so this may move or be relabeled over the next few weeks, but I figured you have all been waiting long enough 😁

This should be sufficient for cases like hiding your enterprise plans and custom deals. Let me know if there are any use cases not covered by this.