feat(dashboard): API to get a dashboard's charts (#12978)

* feat(dashboard): get endpoint for a dashboard's charts

* temporary debugging fetch on the frontend

* attempted fixes

* singular -> plural derp

* plural -> singular derp derp

* docstring changes

* change return, no id

* move log above query

* add get_charts to include_route_methods /)_-)

* add get charts api

* result not response

* refactor test helper function to a mixin

* add test for new endpoint

* fix test when running in isolation

* correct comment

* rename test

* more tests, handle dashboard not found

* simplify test to use new helper function

* remove debugging code from frontend

* update docstring

* attempt a doc fix

* add id to api docs

* fix docs

* use pytest fixture

* why oh why does test order matter here, idk

* writing a schema for the endpoint

* more efficient fetching of charts

* testing tweaks

Co-authored-by: Phillip Kelley-Dotson <pkelleydotson@yahoo.com>

tests/insert_chart_mixin.py

@@ -0,0 +1,61 @@
+# Licensed to the Apache Software Foundation (ASF) under one
+# or more contributor license agreements.  See the NOTICE file
+# distributed with this work for additional information
+# regarding copyright ownership.  The ASF licenses this file
+# to you under the Apache License, Version 2.0 (the
+# "License"); you may not use this file except in compliance
+# with the License.  You may obtain a copy of the License at
+#
+#   http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing,
+# software distributed under the License is distributed on an
+# "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+# KIND, either express or implied.  See the License for the
+# specific language governing permissions and limitations
+# under the License.
+from typing import List, Optional
+
+from superset import ConnectorRegistry, db, security_manager
+from superset.models.slice import Slice
+
+
+class InsertChartMixin:
+    """
+    Implements shared logic for tests to insert charts (slices) in the DB
+    """
+
+    def insert_chart(
+        self,
+        slice_name: str,
+        owners: List[int],
+        datasource_id: int,
+        created_by=None,
+        datasource_type: str = "table",
+        description: Optional[str] = None,
+        viz_type: Optional[str] = None,
+        params: Optional[str] = None,
+        cache_timeout: Optional[int] = None,
+    ) -> Slice:
+        obj_owners = list()
+        for owner in owners:
+            user = db.session.query(security_manager.user_model).get(owner)
+            obj_owners.append(user)
+        datasource = ConnectorRegistry.get_datasource(
+            datasource_type, datasource_id, db.session
+        )
+        slice = Slice(
+            cache_timeout=cache_timeout,
+            created_by=created_by,
+            datasource_id=datasource.id,
+            datasource_name=datasource.name,
+            datasource_type=datasource.type,
+            description=description,
+            owners=obj_owners,
+            params=params,
+            slice_name=slice_name,
+            viz_type=viz_type,
+        )
+        db.session.add(slice)
+        db.session.commit()
+        return slice