[erp5_web] Use web site modification date in must revalidate policy

Ensure that if the web site policy is just set to Must-Revalidate, all documents are updated.
It forces HTTP Cache middleware to refresh their contents.

bt5/erp5_web/SkinTemplateItem/portal_skins/erp5_web/Base_getWebSiteDrivenModificationDate.py

+modification_date = context.getModificationDate()
+
+# Ensure that if the web site policy is just set to Must-Revalidate, all documents are updated.
+# It forces HTTP Cache middleware to refresh there contents.
+is_web_mode = (context.REQUEST.get('current_web_section', None) is not None) or (hasattr(context, 'isWebMode') and context.isWebMode())
+if is_web_mode:
+  modification_date = max(modification_date, context.getWebSectionValue().getModificationDate())
+
+return modification_date

bt5/erp5_web/SkinTemplateItem/portal_skins/erp5_web/Base_getWebSiteDrivenModificationDate.xml

+<?xml version="1.0"?>
+<ZopeData>
+  <record id="1" aka="AAAAAAAAAAE=">
+    <pickle>
+      <global name="PythonScript" module="Products.PythonScripts.PythonScript"/>
+    </pickle>
+    <pickle>
+      <dictionary>
+        <item>
+            <key> <string>Script_magic</string> </key>
+            <value> <int>3</int> </value>
+        </item>
+        <item>
+            <key> <string>_bind_names</string> </key>
+            <value>
+              <object>
+                <klass>
+                  <global name="NameAssignments" module="Shared.DC.Scripts.Bindings"/>
+                </klass>
+                <tuple/>
+                <state>
+                  <dictionary>
+                    <item>
+                        <key> <string>_asgns</string> </key>
+                        <value>
+                          <dictionary>
+                            <item>
+                                <key> <string>name_container</string> </key>
+                                <value> <string>container</string> </value>
+                            </item>
+                            <item>
+                                <key> <string>name_context</string> </key>
+                                <value> <string>context</string> </value>
+                            </item>
+                            <item>
+                                <key> <string>name_m_self</string> </key>
+                                <value> <string>script</string> </value>
+                            </item>
+                            <item>
+                                <key> <string>name_subpath</string> </key>
+                                <value> <string>traverse_subpath</string> </value>
+                            </item>
+                          </dictionary>
+                        </value>
+                    </item>
+                  </dictionary>
+                </state>
+              </object>
+            </value>
+        </item>
+        <item>
+            <key> <string>_params</string> </key>
+            <value> <string></string> </value>
+        </item>
+        <item>
+            <key> <string>id</string> </key>
+            <value> <string>Base_getWebSiteDrivenModificationDate</string> </value>
+        </item>
+      </dictionary>
+    </pickle>
+  </record>
+</ZopeData>

bt5/erp5_web/ToolTemplateItem/caching_policy_manager.xml

@@ -1464,7 +1464,7 @@
       <dictionary>
         <item>
             <key> <string>text</string> </key>
-            <value> <string>python: getattr(object, \'getModificationDate\', object.modified)()</string> </value>
+            <value> <string>python: getattr(object, \'Base_getWebSiteDrivenModificationDate\', object.modified)()</string> </value>
         </item>
       </dictionary>
     </pickle>