(core) Adding import from google drive to the home screen

Summary: Importing from google drive from home screen (also for anonymous users)

Test Plan: Browser tests

Reviewers: dsagal, paulfitz

Reviewed By: dsagal

Differential Revision: https://phab.getgrist.com/D2943

app/client/lib/HomePluginManager.ts

@@ -0,0 +1,57 @@
+import {ClientScope} from 'app/client/components/ClientScope';
+import {SafeBrowser} from 'app/client/lib/SafeBrowser';
+import {LocalPlugin} from 'app/common/plugin';
+import {createRpcLogger, PluginInstance} from 'app/common/PluginInstance';
+
+/**
+ * Home plugins are all plugins that contributes to a general Grist management tasks.
+ * They operate on Grist as a whole, without current document context.
+ * TODO: currently it is used primary for importing documents on home screen and supports
+ * only safeBrowser components without any access to Grist.
+ */
+export class HomePluginManager {
+
+  public pluginsList: PluginInstance[];
+
+  constructor(localPlugins: LocalPlugin[],
+              _untrustedContentOrigin: string,
+              _clientScope: ClientScope) {
+    this.pluginsList = [];
+    for (const plugin of localPlugins) {
+      try {
+        const components = plugin.manifest.components || {};
+        // Home plugins supports only safeBrowser components
+        if (components.safePython || components.unsafeNode) {
+          continue;
+        }
+        // and currently implements only safe imports
+        const importSources = plugin.manifest.contributions.importSources;
+        if (!importSources?.some(i => i.safeHome)) {
+          continue;
+        }
+        const pluginInstance = new PluginInstance(plugin, createRpcLogger(console, `HOME PLUGIN ${plugin.id}:`));
+        const safeBrowser = pluginInstance.safeBrowser = new SafeBrowser(pluginInstance,
+          _clientScope, _untrustedContentOrigin, components.safeBrowser);
+        if (components.safeBrowser) {
+          pluginInstance.rpc.registerForwarder(components.safeBrowser, safeBrowser);
+        }
+        const forwarder = new NotAvailableForwarder();
+        // Block any calls to internal apis.
+        pluginInstance.rpc.registerForwarder('*', {
+          forwardCall: (call) => forwarder.forwardPluginRpc(plugin.id, call),
+          forwardMessage: (msg) => forwarder.forwardPluginRpc(plugin.id, msg),
+        });
+        this.pluginsList.push(pluginInstance);
+      } catch (err) {
+        console.error( // tslint:disable-line:no-console
+          `HomePluginManager: failed to instantiate ${plugin.id}: ${err.message}`);
+      }
+    }
+  }
+}
+
+class NotAvailableForwarder {
+  public async forwardPluginRpc(pluginId: string, msg: any) {
+    throw new Error("This api is not available");
+  }
+}