Add is_deleted field in workspace digest schema

backend/tracim_backend/models/context_models.py

         return slugify(self.workspace.label)
 
     @property
+    def is_deleted(self) -> bool:
+        """
+        Is the workspace deleted ?
+        """
+        return self.workspace.is_deleted
+
+    @property
     def sidebar_entries(self) -> typing.List[WorkspaceMenuEntry]:
         """
         get sidebar entries, those depends on activated apps.

backend/tracim_backend/tests/functional/test_user.py

         assert workspace['workspace_id'] == 1
         assert workspace['label'] == 'Business'
         assert workspace['slug'] == 'business'
+        assert workspace['is_deleted'] is False
         assert len(workspace['sidebar_entries']) == 5
 
         # TODO - G.M - 2018-08-02 - Better test for sidebar entry, make it
         assert sidebar_entry['hexcolor'] == "#ad4cf9"
         assert sidebar_entry['fa_icon'] == "comments-o"
 
-
     def test_api__get_user_workspaces__err_403__unallowed_user(self):
         """
         Check obtain all workspaces reachables for one user

backend/tracim_backend/tests/functional/test_workspaces.py

         assert workspace['slug'] == 'business'
         assert workspace['label'] == 'Business'
         assert workspace['description'] == 'All importants documents'
+        assert workspace['is_deleted'] is False
         assert len(workspace['sidebar_entries']) == 5
 
         # TODO - G.M - 2018-08-02 - Better test for sidebar entry, make it
         assert workspace['slug'] == 'business'
         assert workspace['label'] == 'Business'
         assert workspace['description'] == 'All importants documents'
+        assert workspace['is_deleted'] is False
         assert len(workspace['sidebar_entries']) == 5
 
         # modify workspace
         assert workspace['slug'] == 'superworkspace'
         assert workspace['label'] == 'superworkspace'
         assert workspace['description'] == 'mysuperdescription'
+        assert workspace['is_deleted'] is False
         assert len(workspace['sidebar_entries']) == 5
 
         # after
         assert workspace['slug'] == 'superworkspace'
         assert workspace['label'] == 'superworkspace'
         assert workspace['description'] == 'mysuperdescription'
+        assert workspace['is_deleted'] is False
         assert len(workspace['sidebar_entries']) == 5
 
     def test_api__update_workspace__err_400__empty_label(self) -> None:

backend/tracim_backend/views/core_api/schemas.py

         WorkspaceMenuEntrySchema,
         many=True,
     )
+    is_deleted = marshmallow.fields.Bool(example=False, default=False)
 
     class Meta:
         description = 'Digest of workspace informations'