Add Slack integration

app/Template/config/integrations.php

@@ -0,0 +1,22 @@
+<div class="page-header">
+    <h2><?= t('Integration with third-party services') ?></h2>
+</div>
+
+<form method="post" action="<?= $this->u('config', 'integrations') ?>" autocomplete="off">
+
+    <?= $this->formCsrf() ?>
+
+    <h3><i class="fa fa-slack fa-fw"></i>&nbsp;<?= t('Slack') ?></h3>
+    <div class="listing">
+        <?= $this->formCheckbox('integration_slack_webhook', t('Send notifications to a Slack channel'), 1, $values['integration_slack_webhook'] == 1) ?>
+
+        <?= $this->formLabel(t('Webhook URL'), 'integration_slack_webhook_url') ?>
+        <?= $this->formText('integration_slack_webhook_url', $values, $errors) ?>
+
+        <p class="form-help"><a href="http://kanboard.net/documentation/slack" target="_blank"><?= t('Help on Slack integration') ?></a></p>
+    </div>
+
+    <div class="form-actions">
+        <input type="submit" value="<?= t('Save') ?>" class="btn btn-blue"/>
+    </div>
+</form>

app/Template/config/sidebar.php

@@ -16,6 +16,9 @@
         <li>
             <?= $this->a(t('Currency rates'), 'currency', 'index') ?>
         </li>
+        <li>
+            <?= $this->a(t('Integrations'), 'config', 'integrations') ?>
+        </li>
         <li>
             <?= $this->a(t('Webhooks'), 'config', 'webhook') ?>
         </li>

app/Template/event/task_assignee_change.php

@@ -1,9 +1,15 @@
 <p class="activity-title">
-    <?= e('%s changed the assignee of the task %s to %s',
-            $this->e($author),
-            $this->a(t('#%d', $task['id']), 'task', 'show', array('task_id' => $task['id'], 'project_id' => $task['project_id'])),
-            $this->e($task['assignee_name'] ?: $task['assignee_username'])
-        ) ?>
+    <?php $assignee = $task['assignee_name'] ?: $task['assignee_username'] ?>
+
+    <?php if (! empty($assignee)): ?>
+        <?= e('%s changed the assignee of the task %s to %s',
+                $this->e($author),
+                $this->a(t('#%d', $task['id']), 'task', 'show', array('task_id' => $task['id'], 'project_id' => $task['project_id'])),
+                $this->e($assignee)
+            ) ?>
+    <?php else: ?>
+        <?= e('%s remove the assignee of the task %s', $this->e($author), $this->a(t('#%d', $task['id']), 'task', 'show', array('task_id' => $task['id'], 'project_id' => $task['project_id']))) ?>
+    <?php endif ?>
 </p>
 <p class="activity-description">
     <em><?= $this->e($task['title']) ?></em>