Update code from serverless-next.js to v1.2.0-alpha.3

The package from which much of the code originates was originally called 
serverless-nextjs-component. It's now called lambda-at-edge. The npm 
package name is @sls-next/lambda-at-edge.

This commit integrates the latest changes from that package into 
next-on-netlify.

Author: FinnWoelm

lib/collectNextjsPages.js

@@ -1,5 +1,5 @@
-// Adapted from serverless-next.js (v1.8.0)
-// See original file in serverless-next.js folder.
+// Adapted from @sls-next/lambda-at-edge (v1.8.0)
+// See: https://github.com/danielcondemarin/serverless-next.js/blob/e6732895da50d11dcd296da39d35671b1bd6a33b/packages/lambda-at-edge/src/build.ts
 // Changes:
 // - Function is now collectNextjsPages (was prepareBuildManifests)
 // - Function is now synchronous (used to be async)
@@ -8,13 +8,12 @@
 // - Structure is an array of objects (was an object of objects)
 // - Function now handles custom NextJS distDir
 
-const readPagesManifest       = require('./readPagesManifest')
-const getNetlifyRoute         = require('./getNetlifyRoute')
-const isDynamicRoute          = require("./serverless-next.js/isDynamicRoute")
-const expressifyDynamicRoute  = require("./serverless-next.js/expressifyDynamicRoute")
-const pathToRegexStr          = require("./serverless-next.js/pathToRegexStr")
-
-const isHtmlPage              = p => p.endsWith(".html");
+const readPagesManifest                   = require('./readPagesManifest')
+const getNetlifyRoute                     = require('./getNetlifyRoute')
+const { default: isDynamicRoute }         = require("@sls-next/lambda-at-edge/dist/lib/isDynamicRoute")
+const { default: expressifyDynamicRoute } = require("@sls-next/lambda-at-edge/dist/lib/expressifyDynamicRoute")
+const { default: pathToRegexStr }         = require("@sls-next/lambda-at-edge/dist/lib/pathToRegexStr")
+const isHtmlPage                          = p => p.endsWith(".html");
 
 function collectNextjsPages({ nextDistDir }) {
   const pagesManifest = readPagesManifest({ nextDistDir });

lib/getNetlifyRoute.js

@@ -1,14 +1,15 @@
-// Adapted from serverless-next.js (v1.9.10)
-// https://github.com/danielcondemarin/serverless-next.js/blob/master/packages/serverless-nextjs-component/lib/expressifyDynamicRoute.js
-// The original turns catch-all routes from /[...params] into /:params*
-// This adaptation turns catch-all routes from /[...params] into /:*
-// This is necessary for it to work with Netlify routing.
+// Adapted from @sls-next/lambda-at-edge (v1.2.0-alpha.3)
+// See: https://github.com/danielcondemarin/serverless-next.js/blob/57142970b08e6bc3faf0fc70749b3b0501ad7869/packages/lambda-at-edge/src/lib/expressifyDynamicRoute.ts#L4
+// Changes:
+// - The function now turns catch-all routes from /[...params] into /:*
+//   The original turned catch-all routes from /[...params] into /:params*
+//   The original does not work with Netlify routing.
 
 // converts a nextjs dynamic route /[param]/ -> /:param
 // also handles catch all routes /[...param]/ -> /:*
 module.exports = dynamicRoute => {
   // replace any catch all group first
-  let expressified = dynamicRoute.replace(/\[\.\.\.(.*)]$/, "*");
+  const expressified = dynamicRoute.replace(/\[\.\.\.(.*)]$/, "*");
 
   // now replace other dynamic route groups
   return expressified.replace(/\[(.*?)]/g, ":$1");

lib/readPagesManifest.js

@@ -1,14 +1,13 @@
-// Adapted from serverless-next.js (v1.8.0)
-// See original file in serverless-next.js folder.
+// Adapted from @sls-next/lambda-at-edge (v1.2.0-alpha.3)
+// See: https://github.com/danielcondemarin/serverless-next.js/blob/e6732895da50d11dcd296da39d35671b1bd6a33b/packages/lambda-at-edge/src/build.ts
 // Changes:
 // - The function is now synchronous (it used to by async)
 // - The function now handles custom NextJS distDir
 
-const { join }        = require("path")
-const fse             = require("fs-extra")
-const isDynamicRoute  = require("./serverless-next.js/isDynamicRoute")
-const getSortedRoutes = require("./serverless-next.js/sortedRoutes")
-
+const { join }                      = require("path")
+const fse                           = require("fs-extra")
+const { default: isDynamicRoute }   = require("@sls-next/lambda-at-edge/dist/lib/isDynamicRoute")
+const { getSortedRoutes }  = require("@sls-next/lambda-at-edge/dist/lib/sortedRoutes")
 
 function readPagesManifest({ nextDistDir }) {
   const path = join(nextDistDir, "/serverless/pages-manifest.json");