Only one payment method allowed

[bartoszpietrzak1994]

Scenario: Being unable to add multiple payment methods
    When I create a new order for "jon.snow@the-wall.com" and channel "United States"
    And I select "Cash on Delivery" payment method
    Then adding another payment method should not be possible

Fixes #52

[Zales0123]

:(

[Zales0123]

Formatting gone wrong here :( And I suppose it should be '[data-form-collection="add"]'?

[Zales0123]

It still looks bad (I know, I'm annoying xD)

return $this->getElement('payments')->find('css', '[data-form-collection="add"]') !== null;

or

return
    $this->getElement('payments')->find('css', '[data-form-collection="add"]') !== null
;

It should fit in one line

[Zales0123]

🔫

[wadjeroudi]

@Zales0123 @bartoszpietrzak1994
I think this kind of validation should be added to a different group than sylius or maybe add the constraint in the NewOrderType.
If in your app you have a different workflow for payments, the plugin shouldn't add the validation globally.