Add UI for viewing and cancelling open Zulip invitations.

Lets administrators view a list of open(unconfirmed) invitations and
resend or revoke a chosen invitation.

There are a few changes that we can expect for the future:

  * It is currently possible to invite an email that you have already
    invited, it might make sense to change this behavior.

  * Resend currently sends an invite reminder instead of resending the
    original invite, this is because 'custom_body' was not stored when
    the first invite was sent.

Tweaked in various minor ways, primarily in the backend, by tabbott,
mostly for style consistency with the rest of the codebase.

Fixes: #1180.

zerver/lib/actions.py

@@ -4,6 +4,7 @@ from typing import (
 )
 from mypy_extensions import TypedDict
 
+from django.contrib.contenttypes.models import ContentType
 from django.utils.html import escape
 from django.utils.translation import ugettext as _
 from django.conf import settings
@@ -71,6 +72,7 @@ from django.core.mail import EmailMessage
 from django.utils.timezone import now as timezone_now
 
 from confirmation.models import Confirmation, create_confirmation_link
+from confirmation import settings as confirmation_settings
 from six.moves import filter
 from six.moves import map
 from six import unichr
@@ -3805,6 +3807,82 @@ def do_invite_users(user_profile, invitee_emails, streams, invite_as_admin=False
                                 "invitations to everyone else!"),
                               skipped, sent_invitations=True)
 
+def do_get_user_invites(user_profile):
+    # type: (UserProfile) -> List[Dict[str, Any]]
+    days_to_activate = getattr(settings, 'ACCOUNT_ACTIVATION_DAYS', 7)
+    active_value = getattr(confirmation_settings, 'STATUS_ACTIVE', 1)
+
+    lowest_datetime = timezone_now() - datetime.timedelta(days=days_to_activate)
+    prereg_users = PreregistrationUser.objects.exclude(status=active_value).filter(
+        invited_at__gte=lowest_datetime,
+        referred_by__realm=user_profile.realm)
+
+    invites = []
+
+    for invitee in prereg_users:
+        invites.append(dict(email=invitee.email,
+                            ref=invitee.referred_by.email,
+                            invited=invitee.invited_at.strftime("%Y-%m-%d %H:%M:%S"),
+                            id=invitee.id))
+
+    return invites
+
+def do_revoke_user_invite(invite_id, realm_id):
+    # type: (int, int) -> None
+    try:
+        prereg_user = PreregistrationUser.objects.get(id=invite_id)
+    except PreregistrationUser.DoesNotExist:
+        raise JsonableError(_("Invalid invitation ID."))
+
+    if prereg_user.referred_by.realm_id != realm_id:
+        raise JsonableError(_("Invalid invitation ID."))
+
+    email = prereg_user.email
+
+    # Delete both the confirmation objects and the prereg_user object.
+    # TODO: Probably we actaully want to set the confirmation objects
+    # to a "revoked" status so that we can give the user a better
+    # error message.
+    content_type = ContentType.objects.get_for_model(PreregistrationUser)
+    Confirmation.objects.filter(content_type=content_type,
+                                object_id=prereg_user.id).delete()
+    prereg_user.delete()
+    clear_scheduled_invitation_emails(email)
+
+def do_resend_user_invite_email(invite_id, realm_id):
+    # type: (int, int) -> str
+    try:
+        prereg_user = PreregistrationUser.objects.get(id=invite_id)
+    except PreregistrationUser.DoesNotExist:
+        raise JsonableError(_("Invalid invitation ID."))
+
+    if (prereg_user.referred_by.realm_id != realm_id):
+        raise JsonableError(_("Invalid invitation ID."))
+
+    prereg_user.invited_at = timezone_now()
+    prereg_user.save()
+
+    # sends a invitation reminder since 'custom_body' can not be resent
+    # imported here to avoid import cycle error
+    from zerver.context_processors import common_context
+    clear_scheduled_invitation_emails(prereg_user.email)
+
+    link = create_confirmation_link(prereg_user, prereg_user.referred_by.realm.host, Confirmation.INVITATION)
+    context = common_context(prereg_user.referred_by)
+    context.update({
+        'activate_url': link,
+        'referrer_name': prereg_user.referred_by.full_name,
+        'referrer_email': prereg_user.referred_by.email,
+        'referrer_realm_name': prereg_user.referred_by.realm.name,
+    })
+    send_email(
+        "zerver/emails/invitation_reminder",
+        to_email=prereg_user.email,
+        from_address=FromAddress.NOREPLY,
+        context=context)
+
+    return prereg_user.invited_at.strftime("%Y-%m-%d %H:%M:%S")
+
 def notify_realm_emoji(realm):
     # type: (Realm) -> None
     event = dict(type="realm_emoji", op="update",