Bug 33104: Add the ability to create vendor interfaces

Bug 33104: Add the ability to create vendor interfaces

This patchset is adding the ability to create interfaces for vendors.
An interface is a website, software, or portal that you use to manage orders or
gather statistics from the vendor/organisation.

It will help librarians to keep track of those different information
within Koha.

* new DB table aqbookseller_interfaces(id, vendor_id, type, name, uri,
login, password, account_email, notes)
* new AV category VENDOR_INTERFACE_TYPE with 3 example values ADMIN,
ORDERS, REPORTS
* new pair of Koha classes Koha::Acquisition::Bookseller::Interface[s]
* new method to retrieve the interfaces from the vendor
Koha::Acquisition::Bookseller->interfaces
* Add/Delete interfaces when editing a vendor
* Display the interfaces on the vendor show view

Test plan:
- Add a new vendor
=> Notice the new "Interfaces" block
- Create some interfaces
=> They are display on the vendor show view
=> The password is hashed and can displayed on the demand

QA Note:
The "contacts" code is not very nice and I didn't want to replicate it,
so I went another way and tried to make the code reusable, for further
reutilisation.

Signed-off-by: Jonathan Field <jonathan.field@ptfs-europe.com>
Signed-off-by: Tomas Cohen Arazi <tomascohen@theke.io>