Make Terms of Service editable at runtime by admins (closes #39)

tos.md was baked into the repo and read once at startup, so changing
the terms required a code change and deploy. It's now a Redis-backed
singleton (models/tos.js), editable from a new "Terms of Service" card
on the admin Dashboard, with the bundled tos.md used only as a
one-time seed for new deployments.

- routes/tos.js: GET (any authenticated user) / PUT (app_sso_admin
  only) via /api/tos. Saving can optionally reset every user's
  tos_accepted flag so they're asked to re-accept -- off by default,
  since a wording fix shouldn't re-prompt everyone.
- routes/index.js: /tos and /onboarding now render the live content
  instead of a module-level constant computed once at process start.

nodejs/routes/index.js

@@ -1,17 +1,15 @@
 'use strict';
 
-const fs = require('fs');
 const path = require('path');
 var express = require('express');
 var router = express.Router();
 const moment = require('moment');
 const {marked} = require('marked');
 const {InviteToken, PasswordResetToken} = require('./../models/token');
+const {Tos} = require('../models/tos');
 const conf = require('@simpleworkjs/conf');
 const buildInfo = require('../utils/build_info');
 
-const tosHtml = marked(fs.readFileSync(path.join(__dirname, '../../tos.md'), 'utf8'));
-
 const values ={
   title: conf.environment !== 'production' ? `dev` : '',
   titleIcon: conf.environment !== 'production' ? `<i class="fa-brands fa-dev"></i>` : '',
@@ -44,8 +42,13 @@ router.get('/health', function(req, res) {
   res.json({ status: 'ok' });
 });
 
-router.get('/tos', function(req, res) {
-  res.render('tos', {...values, tosHtml});
+router.get('/tos', async function(req, res, next) {
+  try {
+    const tos = await Tos.getCurrent();
+    res.render('tos', {...values, tosHtml: marked(tos.content), tosUpdatedOnFmt: moment(tos.updated_on, 'x').format('MMMM YYYY')});
+  } catch (error) {
+    next(error);
+  }
 });
 
 // Admin dashboard (stats + recent/inactive users) and Notifications
@@ -61,8 +64,13 @@ router.get('/invites', function(req, res) {
   res.render('invites', {...values});
 });
 
-router.get('/onboarding', function(req, res) {
-  res.render('onboarding', {...values, tosHtml});
+router.get('/onboarding', async function(req, res, next) {
+  try {
+    const tos = await Tos.getCurrent();
+    res.render('onboarding', {...values, tosHtml: marked(tos.content)});
+  } catch (error) {
+    next(error);
+  }
 });
 
 router.get('/', async function(req, res, next) {