[FIX] website, mass_mailing: same field defined twice (#21503)

The ORM does not currently, an probably won't support two fields with
the same name in different modules that do not depend on each other.

This is obviously a nasty hack, but it's the best one can do for a
stable branch.

THIS IS WHY WE HAVE DEPENDENCY MODULES, PEOPLE.

addons/mass_mailing/models/__init__.py

@@ -9,3 +9,4 @@ from . import res_config_settings
 from . import mass_mailing_report
 from . import link_tracker
 from . import res_company
+from . import ir_model_fields

addons/mass_mailing/models/ir_model_fields.py

@@ -0,0 +1,30 @@
+# -*- coding: utf-8 -*-
+# Part of Odoo. See LICENSE file for full copyright and licensing details
+
+from odoo import api, models
+
+
+# This is a nasty hack, targeted for V11 only
+class IrModelFields(models.Model):
+    _inherit = 'ir.model.fields'
+
+    @api.multi
+    def unlink(self):
+        # Prevent the deletion of social_* fields defined in res.company if
+        # the other module is installed
+        social = (
+            'social_facebook',
+            'social_github',
+            'social_googleplus',
+            'social_linkedin',
+            'social_twitter',
+            'social_youtube',
+        )
+
+        self = self.filtered(
+            lambda rec: not (
+                rec.model == 'res.company' and
+                rec.name in social
+            )
+        )
+        return super(IrModelFields, self).unlink()

addons/website/models/__init__.py

@@ -11,3 +11,4 @@ from . import res_company
 from . import res_partner
 from . import web_planner
 from . import res_config_settings
+from . import ir_model_fields

addons/website/models/ir_model_fields.py

@@ -0,0 +1,30 @@
+# -*- coding: utf-8 -*-
+# Part of Odoo. See LICENSE file for full copyright and licensing details
+
+from odoo import api, models
+
+
+# This is a nasty hack, targeted for V11 only
+class IrModelFields(models.Model):
+    _inherit = 'ir.model.fields'
+
+    @api.multi
+    def unlink(self):
+        # Prevent the deletion of social_* fields defined in res.company if
+        # the other module is installed
+        social = (
+            'social_facebook',
+            'social_github',
+            'social_googleplus',
+            'social_linkedin',
+            'social_twitter',
+            'social_youtube',
+        )
+
+        self = self.filtered(
+            lambda rec: not (
+                rec.model == 'res.company' and
+                rec.name in social
+            )
+        )
+        return super(IrModelFields, self).unlink()