[14.0] group_backend: new module and rename group_backend to base_group_backend

As a developer we have to keep in mind using this module and grant a user with 's group is
equivalent to grant 's group everywhere  has been used.

Co-authored-by: Jean-Charles Drubay <jcdrubay@users.noreply.github.com>

base_group_backend/models/res_users.py

@@ -0,0 +1,42 @@
+import logging
+
+from odoo import api, models
+
+_logger = logging.getLogger(__name__)
+
+
+class Users(models.Model):
+    _inherit = "res.users"
+
+
+    # TODO: (franz) make it clear why we test with "." group and why the share = True
+    @api.model
+    def has_group(self, group_ext_id):
+        """While ensuring a user is part of `base.group_user` this code will
+        try if user is in the `base_group_backend.group_backend` group to let access
+        to the odoo backend.
+
+        This code avoid to overwrite a lot of places in controllers from
+        different modules ('portal', 'web', 'base') with hardcoded statement
+        that check if user is part of `base.group_user` group.
+
+        As far `base.group_user` have a lot of default permission this
+        makes hard to maintain proper access right according your business.
+        """
+        res = super().has_group(group_ext_id)
+        if not res and (group_ext_id == "base.group_user"):
+            has_base_group_backend = super().has_group(
+                "base_group_backend.group_backend"
+            )
+            if has_base_group_backend:
+                _logger.warning("Forcing has_group to return True for group_backend")
+            return has_base_group_backend
+        return res
+
+    @api.depends('groups_id')
+    def _compute_share(self):
+        user_group_id = self.env['ir.model.data']._xmlid_to_res_id('base.group_user')
+        backend_user_group_id = self.env['ir.model.data']._xmlid_to_res_id('base_group_backend.group_backend')
+        internal_users = self.filtered_domain([('groups_id', 'in', [user_group_id, backend_user_group_id])])
+        internal_users.share = False
+        (self - internal_users).share = True