add website_membership_signup_required: force to create user before add to cart a membership product

website_membership_signup_required/models/res_config_settings.py

@@ -0,0 +1,12 @@
+# License AGPL-3.0 or later (http://www.gnu.org/licenses/agpl).
+
+from odoo import fields, models
+
+
+class ResConfigSettings(models.TransientModel):
+    _inherit = "res.config.settings"
+
+    membership_signup_required = fields.Boolean(
+        related="website_id.membership_signup_required",
+        readonly=False,
+    )