feat: add functionality to register plugins via http

Also:

- Add functionality for serving the responses from plugins
- Add tests for related methods and routes

Closes #2, #37

src/routes/virtual-plugin-route.ts

@@ -0,0 +1,66 @@
+/*
+ * Copyright (C) 2019 StApps
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Affero General Public License as
+ * published by the Free Software Foundation, either version 3 of the
+ * License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU Affero General Public License for more details.
+ *
+ * You should have received a copy of the GNU Affero General Public License
+ * along with this program.  If not, see <https://www.gnu.org/licenses/>.
+ */
+
+import {
+  SCInternalServerErrorResponse,
+  SCPluginMetaData,
+  SCValidationErrorResponse,
+} from '@openstapps/core';
+import {Request} from 'express';
+import * as got from 'got';
+import {isTestEnvironment, validator} from '../common';
+
+/**
+ * Number of milliseconds after which external request will fail
+ */
+export const EXTERNAL_REQUEST_TIMEOUT = 5000;
+
+/**
+ * Generic route function used to proxy actual requests to plugins
+ *
+ * @param req The request for a plugin resource
+ * @param plugin Meta data of the plugin
+ * @throws {SCInternalServerErrorResponse} On request/response validation or response from the plugin errors
+ */
+export async function virtualPluginRoute(req: Request, plugin: SCPluginMetaData): Promise<object> {
+  let responseBody: object;
+  try {
+    const requestValidation = validator.validate(req.body, plugin.requestSchema);
+    if (requestValidation.errors.length > 0) {
+      throw new SCValidationErrorResponse(requestValidation.errors, isTestEnvironment);
+    }
+    // send the request to the plugin (forward the body) and save the response
+    const pluginResponse = await got.post(
+      plugin.route,
+      {
+        baseUrl: plugin.address,
+        body: req.body,
+        json: true,
+        timeout: EXTERNAL_REQUEST_TIMEOUT,
+      },
+    );
+    responseBody = pluginResponse.body;
+    const responseValidation = validator.validate(responseBody, plugin.responseSchema);
+    if (responseValidation.errors.length > 0) {
+      throw new SCValidationErrorResponse(responseValidation.errors, isTestEnvironment);
+    }
+  } catch (e) {
+    // wrap exact error inside of the internal server error response
+    throw new SCInternalServerErrorResponse(e, isTestEnvironment);
+  }
+
+  return responseBody;
+}