[IMP] rma_sale: portal improvents

- Now it's possible to open several RMAs in a sale order from the portal
- A new comment button has been added to allow the portal user to enter
relevant information like serial numbers o issue description.
- If the requested operation isn't set no RMA will be opened
- The RMA product qty is now a numeric control with limits according to
the qty available to return

[FIX] rma,rma_sale: fix linter errors

rma/models/rma.py

@@ -503,6 +503,7 @@ class Rma(models.Model):
             vals["team_id"] = self.env["rma.team"].search([], limit=1).id
         return super().create(vals)
 
+    @api.multi
     def copy(self, default=None):
         team = super().copy(default)
         for follower in self.message_follower_ids:

rma/models/rma_team.py

@@ -1,7 +1,7 @@
 # Copyright 2020 Tecnativa - Ernesto Tejeda
 # License AGPL-3.0 or later (https://www.gnu.org/licenses/agpl).
 
-from odoo import _, fields, models
+from odoo import _, api, fields, models
 
 
 class RmaTeam(models.Model):
@@ -37,7 +37,9 @@ class RmaTeam(models.Model):
         string='Team Members',
     )
 
+    @api.multi
     def copy(self, default=None):
+        self.ensure_one()
         if default is None:
             default = {}
         if not default.get('name'):

rma/models/stock_picking.py

@@ -1,7 +1,7 @@
 # Copyright 2020 Tecnativa - Ernesto Tejeda
 # License AGPL-3.0 or later (https://www.gnu.org/licenses/agpl).
 
-from odoo import fields, models
+from odoo import api, fields, models
 
 
 class StockPicking(models.Model):
@@ -16,7 +16,9 @@ class StockPicking(models.Model):
         for rec in self:
             rec.rma_count = len(rec.move_lines.mapped('rma_ids'))
 
+    @api.multi
     def copy(self, default=None):
+        self.ensure_one()
         if self.env.context.get('set_rma_picking_type'):
             location_dest_id = default['location_dest_id']
             warehouse = self.env['stock.warehouse'].search(