Making objective_lens a thing

app/templates/admin/augmented_part_detail.html

@@ -44,6 +44,12 @@
           {% else %}—{% endif %}
         </dd>
         <dt>Model suffix</dt><dd>{{ scope_info.model_suffix or "—" }}</dd>
+        <dt>Objective lens diameter</dt>
+        <dd>
+          {% if scope_info.objective_lens_diameter_mm is not none %}
+            {{ scope_info.objective_lens_diameter_mm }} mm
+          {% else %}—{% endif %}
+        </dd>
         <dt>Objective thread</dt><dd>{{ scope_info.objective_thread_pitch or "—" }}</dd>
       </dl>
     </div>