disable mail app to fix the upgrade from 19 to 20

scripts/upgrade

@@ -244,6 +244,15 @@ then
     # Print the current version number of Nextcloud
     exec_occ -V
 
+    # Upgrade may fail if this app is enabled
+    exec_occ app:list | grep -q -w mail
+    mail_app_is_active=$?
+    
+    # Temporary disable the mail app
+    if [ $mail_app_is_active -eq 0 ]; then
+        exec_occ app:disable mail
+    fi
+
     # While the current version is not the last version, do an upgrade
     while [ "$last_version" != "$current_version" ]
     do
@@ -346,6 +355,11 @@ then
     ynh_replace_string --match_string="__DOMAIN__" --replace_string="$domain" --target_file="$nc_conf"
     ynh_replace_string --match_string="__DATADIR__" --replace_string="$datadir" --target_file="$nc_conf"
 
+    # Reneable the mail app
+    if [ $mail_app_is_active -eq 0 ]; then
+        exec_occ app:enable mail
+    fi
+
     # Ensure that UpdateNotification app is disabled
     exec_occ app:disable updatenotification