observers can only add new observees (via the UI) with pairing codes

fixes FOO-934

Why is an observer given a different "add observee" UI when SAML is the
primary auth provider?  Because of PFS-812 -- back in the day, there
were no pairing codes.  Instead, the way to add an observee was to enter
their username and password into Canvas.  This was problematic for a
particular school that used SAML logins -- users didn't _have_ a Canvas
un/pw.  So we built a different flow that forwarded the observer to the
configured SAML auth provider to login as the observee _there_ instead.
Then came pairing codes, and later came
https://gerrit.instructure.com/c/canvas-lms/+/157514 to remove the
pairing code feature flag and make it the only way for an observer to
add observees (in the UI -- the API remained and remains backwards
compatible).  Or at least that seemed to be the intention -- problem is
it actually left the SAML flow behind too, and not only that, it broke
it by changing the shape of the data that gets posted to Canvas (see the
change to `addObservee` in UserObserveesView.coffee).

This commit makes pairing codes the One True Way for an observer to add
observees (again, in the UI), regardless of the account's auth
configuration.

Note that the SAML observer registration flow -- i.e. the half of
PFS-812 that (as far as I know) hasn't been broken since the middle of
2018 -- is kept intact.

test plan:
 - follow repro steps in ticket
 - when you get to the part where you're logged in as an observer and
   you're at Account > Settings > Observing, notice the input is for a
   pairing code, not a username
 - entering a valid pairing code in that box successfully adds the
   corresponding user to your observees list.

Change-Id: I8c875b3824d76786c6d9a787de05c55dfb6dbc6d
Reviewed-on: https://gerrit.instructure.com/c/canvas-lms/+/253344
Tested-by: Service Cloud Jenkins <svc.cloudjenkins@instructure.com>
Reviewed-by: Simon Williams <simon@instructure.com>
QA-Review: August Thornton <august@instructure.com>
Product-Review: August Thornton <august@instructure.com>

app/coffeescripts/views/UserObserveesView.coffee

@@ -19,7 +19,6 @@ import $ from 'jquery'
 import _ from 'underscore'
 import I18n from 'i18n!observees'
 import pairingCodeTemplate from 'jst/PairingCodeUserObservees'
-import extAuthTemplate from 'jst/ExternalAuthUserObservees'
 import itemView from './UserObserveeView'
 import PaginatedCollectionView from './PaginatedCollectionView'
 
@@ -28,11 +27,7 @@ export default class UserObserveesView extends PaginatedCollectionView
   itemView: itemView
   className: 'user-observees'
 
-  template: ->
-    if ENV.AUTH_TYPE == 'saml'
-      extAuthTemplate
-    else
-      pairingCodeTemplate
+  template: pairingCodeTemplate
 
   events:
     'submit .add-observee-form': 'addObservee'

app/controllers/login/saml_controller.rb

@@ -328,8 +328,8 @@ class Login::SamlController < ApplicationController
 
   def observee_validation
     redirect_to
-      @domain_root_account.parent_registration_aac.generate_authn_request_redirect(host: request.host_with_port,
-                                                                                   parent_registration: session[:parent_registration])
+      @domain_root_account.parent_registration_ap.generate_authn_request_redirect(host: request.host_with_port,
+                                                                                  parent_registration: session[:parent_registration])
   end
 
   protected

app/controllers/profile_controller.rb

@@ -483,9 +483,6 @@ class ProfileController < ApplicationController
   private :require_user_for_private_profile
 
   def observees
-    if @domain_root_account.parent_registration?
-      js_env(AUTH_TYPE: @domain_root_account.parent_auth_type)
-    end
     @user ||= @current_user
     set_active_tab 'observees'
     @context = @user.profile if @user == @current_user

app/models/account.rb

@@ -1866,12 +1866,7 @@ class Account < ActiveRecord::Base
     authentication_providers.where(parent_registration: true).exists?
   end
 
-  def parent_auth_type
-    return nil unless parent_registration?
-    parent_registration_aac.auth_type
-  end
-
-  def parent_registration_aac
+  def parent_registration_ap
     authentication_providers.where(parent_registration: true).first
   end
 

app/views/jst/ExternalAuthUserObservees.handlebars

@@ -1,25 +0,0 @@
-<h2>{{#t}}Observing{{/t}}</h2>
-
-<form class="add-observee-form">
-  <div class="row">
-    <div class="span2">
-      <label for="unique_id">
-        {{#t}}Username{{/t}}
-        <input type="text" id="unique_id" name="unique_id">
-      </label>
-    </div>
-  </div>
-  <button type="submit" class="btn btn-primary">
-      <i class="icon-plus" role="presentation"></i>
-      <span class="screenreader-only">Add</span>
-      {{#t}}Student{{/t}}
-  </button>
-</form>
-
-<h3 id="being-observed">{{#t}}Students Being Observed{{/t}}</h3>
-<div class="observees-list-container" aria-busy="false">
-  <ul class="observees-list collectionViewItems" aria-labelledby="being-observed"></ul>
-  <div class="loading-indicator" style="display:none;">
-    <img src="/images/ajax-reload-animated.gif">&nbsp;
-  </div>
-</div>