fix: Add patch to set week_starts_on as "Monday"

frappe/patches.txt

@@ -182,6 +182,7 @@ frappe.patches.v13_0.queryreport_columns
 execute:frappe.reload_doc('core', 'doctype', 'doctype')
 frappe.patches.v13_0.jinja_hook
 frappe.patches.v13_0.update_notification_channel_if_empty
+frappe.patches.v13_0.set_week_starts_on
 frappe.patches.v14_0.drop_data_import_legacy
 frappe.patches.v14_0.rename_cancelled_documents
 frappe.patches.v14_0.copy_mail_data #08.03.21

frappe/patches/v13_0/set_week_starts_on.py

@@ -0,0 +1,7 @@
+import frappe
+
+def execute():
+	frappe.reload_doctype("System Settings")
+	# setting week_starts_on value as "Monday" to avoid breaking change
+	# because before the configuration was introduced, system used to consider "Monday" as start of the week
+	frappe.db.set_value("System Settings", "System Settings", "week_starts_on", "Monday")