Support invites in the registration and login flow

Summary:
Ref T7152. This substantially completes the upstream login flow. Basically, we just cookie you and push you through normal registration, with slight changes:

  - All providers allow registration if you have an invite.
  - Most providers get minor text changes to say "Register" instead of "Login" or "Login or Register".
  - The Username/Password provider changes to just a "choose a username" form.
  - We show the user that they're accepting an invite, and who invited them.

Then on actual registration:

  - Accepting an invite auto-verifies the address.
  - Accepting an invite auto-approves the account.
  - Your email is set to the invite email and locked.
  - Invites get to reassign nonprimary, unverified addresses from other accounts.

But 98% of the code is the same.

Test Plan:
  - Accepted an invite.
  - Verified a new address on an existing account via invite.
  - Followed a bad invite link.
  - Tried to accept a verified invite.
  - Reassigned an email by accepting an unverified, nonprimary invite on a new account.
  - Verified that reassigns appear in the activity log.

{F291493}
{F291494}
{F291495}
{F291496}
{F291497}
{F291498}
{F291499}

Reviewers: btrahan

Reviewed By: btrahan

Subscribers: epriestley

Maniphest Tasks: T7152

Differential Revision: https://secure.phabricator.com/D11737

src/applications/auth/controller/PhabricatorAuthController.php

@@ -108,6 +108,9 @@ abstract class PhabricatorAuthController extends PhabricatorController {
 
     // Clear the client ID / OAuth state key.
     $request->clearCookie(PhabricatorCookies::COOKIE_CLIENTID);
+
+    // Clear the invite cookie.
+    $request->clearCookie(PhabricatorCookies::COOKIE_INVITE);
   }
 
   private function buildLoginValidateResponse(PhabricatorUser $user) {
@@ -246,4 +249,57 @@ abstract class PhabricatorAuthController extends PhabricatorController {
     return array($account, $provider, null);
   }
 
+  protected function loadInvite() {
+    $invite_cookie = PhabricatorCookies::COOKIE_INVITE;
+    $invite_code = $this->getRequest()->getCookie($invite_cookie);
+    if (!$invite_code) {
+      return null;
+    }
+
+    $engine = id(new PhabricatorAuthInviteEngine())
+      ->setViewer($this->getViewer())
+      ->setUserHasConfirmedVerify(true);
+
+    try {
+      return $engine->processInviteCode($invite_code);
+    } catch (Exception $ex) {
+      // If this fails for any reason, just drop the invite. In normal
+      // circumstances, we gave them a detailed explanation of any error
+      // before they jumped into this workflow.
+      return null;
+    }
+  }
+
+  protected function renderInviteHeader(PhabricatorAuthInvite $invite) {
+    $viewer = $this->getViewer();
+
+    $invite_author = id(new PhabricatorPeopleQuery())
+      ->setViewer($viewer)
+      ->withPHIDs(array($invite->getAuthorPHID()))
+      ->needProfileImage(true)
+      ->executeOne();
+
+    // If we can't load the author for some reason, just drop this message.
+    // We lose the value of contextualizing things without author details.
+    if (!$invite_author) {
+      return null;
+    }
+
+    $invite_item = id(new PHUIObjectItemView())
+      ->setHeader(pht('Welcome to Phabricator!'))
+      ->setImageURI($invite_author->getProfileImageURI())
+      ->addAttribute(
+        pht(
+          '%s has invited you to join Phabricator.',
+          $invite_author->getFullName()));
+
+    $invite_list = id(new PHUIObjectItemListView())
+      ->addItem($invite_item)
+      ->setFlush(true);
+
+    return id(new PHUIBoxView())
+      ->addMargin(PHUI::MARGIN_LARGE)
+      ->appendChild($invite_list);
+  }
+
 }