API interfaces

[chriskapp]

We need a way to describe a general API interface. I.e. we have two specifications which describe a service for sending mails. It would be great if there is a way to create an interface to describe a general mail sending service. Both concrete specifications could then implement such an mail sending interface. An interface basically defines operations and types but without actual HTTP method and path mapping so that this can be vendor specific. It would be also great if we could create a type mapping where the concrete specification type maps to an interface type, through this even the property names of each JSON object could be vendor independent.

In the end this would makes it easier to create vendor independent code since you can easily swap the vendor SDK in case you want to switch the mail sending service. Of course like always with interfaces you cant use vendor specific features which might be a problem in some cases but then you are bound to this specific vendor.

At the code generator we could also generate an actual interface which is then implemented by the client SDK. A problem is maybe the grouping features since we would need to create different interfaces for each tag.