(core) Skip /welcome/user page for new users

Summary:
Since the new Grist sign-up page has a required field for
name, we can now skip the welcome page asking for the
same thing. Code and tests that can be removed later are
marked with TODOs.

Test Plan: Browser tests.

Reviewers: paulfitz

Reviewed By: paulfitz

Differential Revision: https://phab.getgrist.com/D3266

app/client/ui/WelcomePage.ts

@@ -84,6 +84,7 @@ export class WelcomePage extends Disposable {
     ));
   }
 
+  // TODO: This can be removed, since the 'user' page is no longer part of any flow.
   private _buildNameForm(owner: MultiHolder) {
     let inputEl: HTMLInputElement;
     let form: HTMLFormElement;
@@ -235,6 +236,8 @@ export class WelcomePage extends Disposable {
 
   /**
    * Builds a form to ask the new user a few questions.
+   *
+   * TODO: This can be removed, since the 'info' page is no longer part of any flow.
    */
   private _buildInfoForm(owner: MultiHolder) {
     const allFilled = Observable.create(owner, false);