3scale application apply/create: cannot create an application if another app with the same user_key / app_id exists for another service

[nmasse-itix]

Current behavior

Create a service svc1, a plan and an app:

$ 3scale import openapi -d 3scale-saas -t svc1 https://raw.githubusercontent.com/rh-integration/3scale-toolbox-jenkins-samples/master/saas-usecase-apikey/swagger.yaml
Created service id: 2555417814790, name: Beer Catalog API
Service proxy updated
destroying all mapping rules
Created GET /api/beer/{name}$ endpoint
Created GET /api/beer/findByStatus/{status}$ endpoint
Created GET /api/beer$ endpoint

$ 3scale application-plan apply 3scale-saas svc1 test --name=test 
Applied application plan id: 2357356101963; Default: false

$ 3scale application apply 3scale-saas my-super-secret-key --account=nmasse+test@redhat.com --name="Test Application" --plan=test --service=svc1
Applied application id: 1409618476816

Create a service svc2, a plan and an app:

$ 3scale import openapi -d 3scale-saas -t svc2 https://raw.githubusercontent.com/rh-integration/3scale-toolbox-jenkins-samples/master/saas-usecase-apikey/swagger.yaml
Created service id: 2555417814794, name: Beer Catalog API
destroying all mapping rules
Created GET /api/beer/{name}$ endpoint
Created GET /api/beer/findByStatus/{status}$ endpoint
Created GET /api/beer$ endpoint
Service proxy updated

$ 3scale application-plan apply 3scale-saas svc2 test --name=test 
Applied application plan id: 2357356101966; Default: false

$ 3scale application apply 3scale-saas my-super-secret-key --account=nmasse+test@redhat.com --name="Test Application" --plan=test --service=svc2
Applied application id: 1409618476816

As you can see, the last call to application-plan apply update the application of svc1 instead of creating a new application for svc2.

Expected behavior

The last call to application-plan apply creates a new application for svc2:

$ 3scale application apply 3scale-saas my-super-secret-key --account=nmasse+test@redhat.com --name="Test Application" --plan=test --service=svc2
Applied application id: 123456

(When calling /admin/api/applications/find.json, specify the service_id to restrict the search to one specific service.)