HDX-9420 display alert if user tries to go back to page b

ckanext-hdx_theme/ckanext/hdx_theme/fanstatic/onboarding/prevent-back-button.js

@@ -0,0 +1,12 @@
+window.history.pushState({page: 2}, null, null);
+
+window.onpopstate = function (event) {
+  if (event) {
+    var r = confirm('Hold on! Your data has already been saved. Are you sure you want to go back to the previous page and reload the signup process?');
+    if (r === true) {
+      history.back();
+    } else {
+      window.history.pushState({page: 2}, '', '');
+    }
+  }
+}

ckanext-hdx_theme/ckanext/hdx_theme/fanstatic/webassets.yml

@@ -126,6 +126,12 @@ hdx-onboarding-scripts:
     - onboarding/came-from-input.js
     - onboarding/confirm-page-leave.js
 
+prevent-back-button:
+  <<: *common-js
+  output: ckanext-hdx_theme/%(version)s_prevent-back-button.js
+  contents:
+    - onboarding/prevent-back-button.js
+
 search-scripts:
   <<: *common-js
   output: ckanext-hdx_theme/%(version)s_search-scripts.js

ckanext-hdx_theme/ckanext/hdx_theme/templates/onboarding/signup/verify-email.html

@@ -1,5 +1,10 @@
 {% extends "onboarding/base.html" %}
 
+{% block scripts %}
+  {{ super() }}
+  {% asset 'hdx_theme/prevent-back-button' %}
+{% endblock %}
+
 {% set CONST = h.HDX_CONST('UI_CONSTANTS')['ONBOARDING']['VERIFY_EMAIL'] %}
 
 {% block subtitle %}{{ _('User info') }}{% endblock %}