Add missing x-api-model attribute to make sure we correctly validate the API endpoint input payload.
Add missing x-api-model attribute to make sure we correctly validate the
API endpoint input payload.

nzlosh/st2,StackStorm/st2,Plexxi/st2,StackStorm/st2,nzlosh/st2,StackStorm/st2,StackStorm/st2,nzlosh/st2,Plexxi/st2,Plexxi/st2,nzlosh/st2,Plexxi/st2