slapos_erp5: Check if OAuth is really configured before show Google/Facebook login buttons

    This prevent not configured sites show the sign-in buttons w/o proper configuration, in other words, broken buttons.

master/bt5/slapos_erp5/SkinTemplateItem/portal_skins/slapos_base/ERP5Site_getAvailableOAuthLoginList.py

+oauth_login_list = []
+
+portal_skin = context.getPortalObject().portal_skins
+
+if getattr(portal_skin, "erp5_oauth_google_login", None) is not None:
+  connector = context.ERP5Site_getGoogleConnector()
+  if connector is not None and connector[0].getClientId() is not None:
+    oauth_login_list.append("google")
+
+if getattr(portal_skin, "erp5_oauth_facebook_login", None) is not None:
+  connector = context.ERP5Site_getFacebookConnector()
+  if connector is not None and connector[0].getClientId() is not None:
+    oauth_login_list.append("facebook")
+
+if getattr(portal_skin, "erp5_openid_connect_client", None) is not None:
+  oauth_login_list.append("openidconnect")
+
+return oauth_login_list

master/bt5/slapos_erp5/SkinTemplateItem/portal_skins/slapos_base/ERP5Site_getAvailableOAuthLoginList.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>_proxy_roles</string> </key>
+            <value>
+              <tuple>
+                <string>Manager</string>
+              </tuple>
+            </value>
+        </item>
+        <item>
+            <key> <string>id</string> </key>
+            <value> <string>ERP5Site_getAvailableOAuthLoginList</string> </value>
+        </item>
+      </dictionary>
+    </pickle>
+  </record>
+</ZopeData>