feat: add checkbox and milestone components for value change notifications

Author: tanhongit

resources/views/md/field_types/checkbox.blade.php

@@ -0,0 +1,9 @@
+@if(isset($fromValue) && $fromValue !== $toValue)
+    **`{{ $fieldName }}`** has been {{ $toValue ? 'checked' : 'unchecked' }}.
+@elseif ($toValue === true)
+    **`{{ $fieldName }}`** has been checked.
+@elseif ($toValue === false)
+    **`{{ $fieldName }}`** has been unchecked.
+@else
+    **`{{ $fieldName }}`** has been set to {{ $toValue ? '✅' : '❌' }}.
+@endif

resources/views/md/field_types/milestone.blade.php

@@ -0,0 +1,13 @@
+@if($fromValue != null && $toValue != null)
+    **`{{ $fieldName }}`** has been updated:
+    - From: **`{{ $fromValue['title'] }}`**
+    - To: **`{{ $toValue['title'] }}`**
+@elseif ($toValue == null)
+    **`{{ $fieldName }}`** has been removed from the issue.
+@else
+    **`{{ $fieldName }}`** has been set to **`{{ $toValue['title'] }}`**.
+@endif
+
+@if(($toValue['due_on'] ?? null) && ($toValue['due_on'] !== ($fromValue['due_on'] ?? null)))
+    - Due date: {{ format_date($toValue['due_on'], 'Y-m-d') }}
+@endif