Adds rudimentary validation to user invite

refs TryGhost#5652

- with these changes, validation appears, but doesn't properly prevent closing the modal
- this needs revisiting at some point

core/client/app/controllers/modals/invite-new-user.js

@@ -1,8 +1,11 @@
 import Ember from 'ember';
+import ValidationEngine from 'ghost/mixins/validation-engine';
 
-export default Ember.Controller.extend({
+export default Ember.Controller.extend(ValidationEngine, {
     notifications: Ember.inject.service(),
 
+    validationType: 'signup',
+
     role: null,
     authorRole: null,
 
@@ -42,13 +45,13 @@ export default Ember.Controller.extend({
         confirmAccept: function () {
             var email = this.get('email'),
                 role = this.get('role'),
+                validationErrors = this.get('errors.messages'),
                 self = this,
                 newUser;
 
             // reset the form and close the modal
-            self.set('email', '');
-            self.set('role', self.get('authorRole'));
-            self.send('closeModal');
+            this.set('email', '');
+            this.set('role', self.get('authorRole'));
 
             this.store.find('user').then(function (result) {
                 var invitedUser = result.findBy('email', email);
@@ -82,7 +85,13 @@ export default Ember.Controller.extend({
                         // save is overridden in order to validate, we probably
                         // want to use inline-validations here and only show an
                         // alert if we have an actual error
-                        self.get('notifications').showErrors(errors);
+                        if (errors) {
+                            self.get('notifications').showErrors(errors);
+                        } else if (validationErrors) {
+                            self.get('notifications').showAlert(validationErrors.toString(), {type: 'error'});
+                        }
+                    }).finally(function () {
+                        self.get('errors').clear();
                     });
                 }
             });

core/client/app/routes/team/user.js

@@ -46,10 +46,16 @@ var TeamUserRoute = AuthenticatedRoute.extend(styleBody, CurrentUserSettings, {
             model.rollback();
         }
 
+        model.get('errors').clear();
+
         this._super();
     },
 
     actions: {
+        didTransition: function () {
+            this.modelFor('team.user').get('errors').clear();
+        },
+
         save: function () {
             this.get('controller').send('save');
         }

core/client/app/templates/modals/invite-new-user.hbs

@@ -2,11 +2,12 @@
     title="Invite a New User" confirm=confirm class="invite-new-user"}}
 
     <fieldset>
-        <div class="form-group">
+        {{#gh-form-group errors=errors hasValidated=hasValidated property="email"}}
             <label for="new-user-email">Email Address</label>
-            {{input enter="confirmAccept" class="gh-input email" id="new-user-email" type="email" placeholder="Email Address" name="email" autofocus="autofocus"
-            autocapitalize="off" autocorrect="off" value=email}}
-        </div>
+            {{gh-input enter="confirmAccept" class="email" id="new-user-email" type="email" placeholder="Email Address" name="email" autofocus="autofocus"
+            autocapitalize="off" autocorrect="off" value=email focusOut=(action "validate" "email")}}
+            {{gh-error-message errors=errors property="email"}}
+        {{/gh-form-group}}
 
         <div class="form-group for-select">
             <label for="new-user-role">Role</label>