Adapt app-driven entity page

Addresses the changes required after merging #2076. The Sentry plugin
now defines a router and the widget will be displayed as a tab.

plugins/sentry/src/components/Router.tsx

@@ -0,0 +1,49 @@
+/*
+ * Copyright 2020 Spotify AB
+ *
+ * Licensed 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.
+ */
+import React from 'react';
+import { Entity } from '@backstage/catalog-model';
+import { Routes, Route } from 'react-router';
+import { WarningPanel } from '@backstage/core';
+import { SentryPluginWidget } from './SentryPluginWidget/SentryPluginWidget';
+
+const SENTRY_ANNOTATION = 'sentry.io/project-id';
+
+const isPluginApplicableToEntity = (entity: Entity) =>
+  Boolean(entity.metadata.annotations?.[SENTRY_ANNOTATION]) &&
+  entity.metadata.annotations?.[SENTRY_ANNOTATION] !== '';
+
+export const Router = ({ entity }: { entity: Entity }) =>
+  !isPluginApplicableToEntity(entity) ? (
+    <WarningPanel title="Sentry plugin:">
+      `entity.metadata.annotations['
+      {SENTRY_ANNOTATION}']` key is missing on the entity.{' '}
+    </WarningPanel>
+  ) : (
+    <Routes>
+      <Route
+        path="/"
+        element={
+          <SentryPluginWidget
+            sentryProjectId={
+              entity.metadata.annotations?.[SENTRY_ANNOTATION] || ''
+            }
+            statsFor="24h"
+          />
+        }
+      />
+      )
+    </Routes>
+  );

plugins/sentry/src/index.ts

@@ -15,4 +15,5 @@
  */
 
 export { plugin } from './plugin';
+export { Router } from './components/Router';
 export { SentryPluginWidget as SentryIssuesWidget } from './components/SentryPluginWidget/SentryPluginWidget';