Is your feature request related to a problem?

For a better architecture, reorganize fields in BO > shop parameters > product settings page in the following order:

A while ago, we converted API controller specs into requests specs, see #2052. But those specs still have references from their old "life" that we can clean a little bit with a small effort.

In fact, their filenames still have the _controller_ part, which makes no sense now. Eg. solidus/api/spec/requests/spree/api/addresses_controller_spec.rb

Also, they contain references to the previo

Is your feature request related to a problem? Please describe.
Currently, if the developer wants to register a new admin account, it doesn't let it do that because sendgrid API keys are needed. Remove this dependency for local, and switch to using an identical emailService which uses Nodemailer (Gmail option preferred) since Nodemailer is free. Maybe feature flag this property

**Describe

The package creation/splitting is heavily dependant on zones. Prevent deletion of the last available zone.