(core) move home server into core

Summary: This moves enough server material into core to run a home server.  The data engine is not yet incorporated (though in manual testing it works when ported).

Test Plan: existing tests pass

Reviewers: dsagal

Reviewed By: dsagal

Differential Revision: https://phab.getgrist.com/D2552

app/server/lib/expressWrap.ts

@@ -0,0 +1,36 @@
+import {RequestWithLogin} from 'app/server/lib/Authorizer';
+import * as log from 'app/server/lib/log';
+import * as express from 'express';
+
+/**
+ * Wrapper for async express endpoints to catch errors and forward them to the error handler.
+ */
+export function expressWrap(callback: express.RequestHandler): express.RequestHandler {
+  return async (req, res, next) => {
+    try {
+      await callback(req, res, next);
+    } catch (err) {
+      next(err);
+    }
+  };
+}
+
+/**
+ * Error-handling middleware that responds to errors in json. The status code is taken from
+ * error.status property (for which ApiError is convenient), and defaults to 500.
+ */
+export const jsonErrorHandler: express.ErrorRequestHandler = (err, req, res, next) => {
+  const mreq = req as RequestWithLogin;
+  log.warn("Error during api call to %s: (%s) user %d params %s body %s", req.path, err.message,
+           mreq.userId,
+           JSON.stringify(req.params), JSON.stringify(req.body));
+  res.status(err.status || 500).json({error: err.message || 'internal error',
+                                      details: err.details});
+};
+
+/**
+ * Middleware that responds with a 404 status and a json error object.
+ */
+export const jsonNotFoundHandler: express.RequestHandler = (req, res, next) => {
+  res.status(404).json({error: `not found: ${req.url}`});
+};