Scope Credit Card API to user_id.

Fixes #5232
fix failing api spec. specifying additional params for line_items. all green now.
Make reimbursement credit descriptions more descriptive

* Use the creditable's class name

Fixes #5242
Add an optional breadcrumb class.

I had to add a custom style for `ul` tag of breadcrumb. Hope this would solve my issue.
Fixes #5241
Use string for key. Fixes #5243
Set promo adjustment to 0 when not actionable

If an order qualifies for a line item promotion due to meeting some
condition (say, 10% off 5 or more), and the cart is updated so that the
line item promotion no longer qualifies, this will ensure that the line
item promotion is set to zero.

There is additionally some changes to hide promotions which are zero, as
they're not super interesting. The promotions are zero-d out and hidden
so that if at some point in the future the order re-qualifies, the
amount will be set correctly.

Conflicts:
	frontend/app/views/spree/orders/_form.html.erb

Closes #5245
Create tax adjustment label with inclusive information if applicable
Fixes #5244