[FIX] mail_gateway: dummy compatibility with m2m fields

Other OCA modules extending the composer add m2m fields with fixed
relations. To avoid a glue module we try for the moment to add those
manually.

TT51108

mail_gateway/models/res_partner.py

@@ -67,6 +67,8 @@ class ResPartnerGatewayChannel(models.Model):
     )
 
     def name_get(self):
+        # Be able to tell to which partner belongs the gateway partner channel
+        # e.g.: picking it from a selector
         result = []
         origin = super().name_get()
         if not self.env.context.get("mail_gateway_partner_info", False):

mail_gateway/wizards/mail_compose_gateway_message.py

@@ -28,7 +28,6 @@ class MailComposeGatewayMessage(models.TransientModel):
         "attachment_id",
         "Attachments",
     )
-
     partner_ids = fields.Many2many(
         "res.partner",
         "mail_compose_gateway_message_res_partner_rel",
@@ -37,6 +36,30 @@ class MailComposeGatewayMessage(models.TransientModel):
         "Additional Contacts",
         domain=lambda r: r._partner_ids_domain(),
     )
+    # Dummy compatibility with other OCA modules
+    # OCA/mail_attach_existing_attachment
+    object_attachment_ids = fields.Many2many(
+        comodel_name="ir.attachment",
+        relation="mail_compose_gateway_message_ir_attachments_object_rel",
+        column1="wizard_id",
+        column2="attachment_id",
+        string="Object Attachments",
+    )
+    # OCA/mail_composer_cc_bcc
+    partner_cc_ids = fields.Many2many(
+        comodel_name="res.partner",
+        relation="mail_compose_gateway_message_res_partner_cc_rel",
+        column1="wizard_id",
+        column2="partner_id",
+        string="Cc",
+    )
+    partner_bcc_ids = fields.Many2many(
+        comodel_name="res.partner",
+        relation="mail_compose_gateway_message_res_partner_bcc_rel",
+        column1="wizard_id",
+        column2="partner_id",
+        string="Bcc",
+    )
 
     def get_mail_values(self, res_ids):
         self.ensure_one()

mail_gateway/wizards/mail_compose_gateway_message.xml

@@ -8,13 +8,17 @@
         <field name="inherit_id" ref="mail.email_compose_message_wizard_form" />
         <field name="mode">primary</field>
         <field name="arch" type="xml">
+            <label for="partner_ids" position="attributes">
+                <attribute name="invisible">1</attribute>
+            </label>
             <field name="partner_ids" position="attributes">
                 <attribute name="invisible">1</attribute>
             </field>
-            <field name="body" position="before">
+            <field name="subject" position="before">
                 <field name="wizard_partner_ids" invisible="1" />
                 <field
                     name="wizard_channel_ids"
+                    string="Gateways"
                     widget="many2many_tags"
                     context="{'mail_gateway_partner_info': 1}"
                     domain="[('partner_id', 'in', wizard_partner_ids)]"