Add linking app setup API views and tests.

mayan/apps/linking/apps.py

@@ -12,6 +12,7 @@ from common import (
 )
 from common.widgets import two_state_template
 from navigation import SourceColumn
+from rest_api.classes import APIEndPoint
 
 from .links import (
     link_smart_link_create, link_smart_link_condition_create,
@@ -35,6 +36,8 @@ class LinkingApp(MayanAppConfig):
     def ready(self):
         super(LinkingApp, self).ready()
 
+        APIEndPoint(app=self, version_string='1')
+
         Document = apps.get_model(
             app_label='documents', model_name='Document'
         )