Add custom routes to pages router (#7231)

* added custom routes

* fixed docs typos

* added page.customRoutes config validation

* added 404 response if missing custom route response

* added docs

* minor README formatting

* added CHANGELOG entry

* fixed bug in definitions builder that did not recognize array of custom type

* added missing route handler definition

* fixed custom routes definition

src/Options/Definitions.js

@@ -425,6 +425,12 @@ module.exports.ParseServerOptions = {
   },
 };
 module.exports.PagesOptions = {
+  customRoutes: {
+    env: 'PARSE_SERVER_PAGES_CUSTOM_ROUTES',
+    help: 'The custom routes.',
+    action: parsers.arrayParser,
+    default: [],
+  },
   customUrls: {
     env: 'PARSE_SERVER_PAGES_CUSTOM_URLS',
     help: 'The URLs to the custom pages.',
@@ -481,6 +487,23 @@ module.exports.PagesOptions = {
     default: {},
   },
 };
+module.exports.PagesRoute = {
+  handler: {
+    env: 'PARSE_SERVER_PAGES_ROUTE_HANDLER',
+    help: 'The route handler that is an async function.',
+    required: true,
+  },
+  method: {
+    env: 'PARSE_SERVER_PAGES_ROUTE_METHOD',
+    help: "The route method, e.g. 'GET' or 'POST'.",
+    required: true,
+  },
+  path: {
+    env: 'PARSE_SERVER_PAGES_ROUTE_PATH',
+    help: 'The route path.',
+    required: true,
+  },
+};
 module.exports.PagesCustomUrlsOptions = {
   emailVerificationLinkExpired: {
     env: 'PARSE_SERVER_PAGES_CUSTOM_URL_EMAIL_VERIFICATION_LINK_EXPIRED',