Change user deletion warning to be more explicit.

Issue #4583
- If a user has posts, show the count in the deletion warning.

ghost/admin/controllers/modals/delete-user.js

@@ -1,4 +1,24 @@
-var DeleteUserController = Ember.Controller.extend({
+var DeleteUserController = Ember.ObjectController.extend({
+    userPostCount: Ember.computed('id', function () {
+        var promise,
+            query = {
+                author: this.get('slug'),
+                status: 'all'
+            };
+
+        promise = this.store.find('post', query).then(function (results) {
+            return results.meta.pagination.total;
+        });
+
+        return Ember.Object.extend(Ember.PromiseProxyMixin, {
+            count: Ember.computed.alias('content'),
+
+            inflection: Ember.computed('count', function () {
+                return this.get('count') > 1 ? 'posts' : 'post';
+            })
+        }).create({promise: promise});
+    }),
+
     actions: {
         confirmAccept: function () {
             var self = this,

ghost/admin/templates/modals/delete-user.hbs

@@ -1,7 +1,12 @@
 {{#gh-modal-dialog action="closeModal" showClose=true type="action" style="wide,centered" animation="fade"
     title="Are you sure you want to delete this user?" confirm=confirm}}
 
-    <p>All posts and associated data will also be deleted. There is no way to recover this data.
+    {{#unless userPostCount.isPending}}
-    </p>
+        {{#if userPostCount.count}}
+            <strong>WARNING:</strong> <span class="red">This user is the author of {{userPostCount.count}} {{userPostCount.inflection}}.</span> All posts and user data will be deleted. There is no way to recover this.
+        {{else}}
+            <strong>WARNING:</strong> All user data will be deleted. There is no way to recover this.
+        {{/if}}
+    {{/unless}}
 
 {{/gh-modal-dialog}}