Add ‘optional text’ macro

This pattern of value or grey text saying `None` is common enough in our
app that we should codify it into a pattern. Which this commit does.

app/templates/components/table.html

@@ -92,6 +92,13 @@
   {% endcall %}
 {%- endmacro %}
 
+{% macro optional_text_field(text, default=None) -%}
+  {{ text_field(
+    text or default,
+    status='' if text else 'default'
+  ) }}
+{%- endmacro %}
+
 {% macro link_field(text, link) -%}
   {% call field() %}
     <a href="{{ link }}">{{ text }}</a>