[IMP] website: make cover_properties a mixin field

Next commit will add new cover properties entries for the bg color.
Still, we want a default `bg-primary` class. Instead of addind 3 new default
value in existing cover_property fields, the chance is taken to make a mixin
out of that field to avoid code duplication.

task-2144335

addons/website/models/mixins.py

 # -*- coding: utf-8 -*-
 # Part of Odoo. See LICENSE file for full copyright and licensing details.
 
+import json
 import logging
 
 
@@ -97,6 +98,21 @@ class SeoMetadata(models.AbstractModel):
         }
 
 
+class WebsiteCoverPropertiesMixin(models.AbstractModel):
+
+    _name = 'website.cover_properties.mixin'
+    _description = 'Cover Properties Website Mixin'
+
+    cover_properties = fields.Text('Cover Properties', default=lambda s: json.dumps(s._default_cover_properties()))
+
+    def _default_cover_properties(self):
+        return {
+            "background-image": "none",
+            "opacity": "0.2",
+            "resize_class": "o_half_screen_height",
+        }
+
+
 class WebsiteMultiMixin(models.AbstractModel):
 
     _name = 'website.multi.mixin'

addons/website_blog/models/website_blog.py

@@ -14,16 +14,13 @@ from odoo.tools import html2plaintext
 class Blog(models.Model):
     _name = 'blog.blog'
     _description = 'Blog'
-    _inherit = ['mail.thread', 'website.seo.metadata', 'website.multi.mixin']
+    _inherit = ['mail.thread', 'website.seo.metadata', 'website.multi.mixin', 'website.cover_properties.mixin']
     _order = 'name'
 
     name = fields.Char('Blog Name', required=True, translate=True)
     subtitle = fields.Char('Blog Subtitle', translate=True)
     active = fields.Boolean('Active', default=True)
     content = fields.Html('Content', translate=html_translate, sanitize=False)
-    cover_properties = fields.Text(
-        'Cover Properties',
-        default='{"background-image": "none", "opacity": "0.2", "resize_class": "o_half_screen_height"}')
 
     def write(self, vals):
         res = super(Blog, self).write(vals)
@@ -114,7 +111,7 @@ class BlogTag(models.Model):
 class BlogPost(models.Model):
     _name = "blog.post"
     _description = "Blog Post"
-    _inherit = ['mail.thread', 'website.seo.metadata', 'website.published.multi.mixin']
+    _inherit = ['mail.thread', 'website.seo.metadata', 'website.published.multi.mixin', 'website.cover_properties.mixin']
     _order = 'id DESC'
     _mail_post_access = 'read'
 
@@ -131,9 +128,6 @@ class BlogPost(models.Model):
     subtitle = fields.Char('Sub Title', translate=True)
     author_id = fields.Many2one('res.partner', 'Author', default=lambda self: self.env.user.partner_id)
     active = fields.Boolean('Active', default=True)
-    cover_properties = fields.Text(
-        'Cover Properties',
-        default='{"background-image": "none", "opacity": "0.2", "resize_class": "o_half_screen_height"}')
     blog_id = fields.Many2one('blog.blog', 'Blog', required=True, ondelete='cascade')
     tag_ids = fields.Many2many('blog.tag', string='Tags')
     content = fields.Html('Content', default=_default_content, translate=html_translate, sanitize=False)

addons/website_event/models/event_event.py

@@ -19,7 +19,7 @@ class EventType(models.Model):
 
 class Event(models.Model):
     _name = 'event.event'
-    _inherit = ['event.event', 'website.seo.metadata', 'website.published.multi.mixin']
+    _inherit = ['event.event', 'website.seo.metadata', 'website.published.multi.mixin', 'website.cover_properties.mixin']
 
     # description
     subtitle = fields.Char('Event Subtitle', translate=True)
@@ -27,9 +27,6 @@ class Event(models.Model):
     is_participating = fields.Boolean("Is Participating", compute="_compute_is_participating")
     # website
     website_published = fields.Boolean(tracking=True)
-    cover_properties = fields.Text(
-        'Cover Properties',
-        default='{"background-image": "none", "opacity": "0.4", "resize_class": "o_half_screen_height"}')
     website_menu = fields.Boolean(
         'Dedicated Menu', copy=False,
         help="Creates menus Introduction, Location and Register on the page "
@@ -59,6 +56,11 @@ class Event(models.Model):
         if self.event_type_id:
             self.website_menu = self.event_type_id.website_menu
 
+    def _default_cover_properties(self):
+        res = super()._default_cover_properties()
+        res['opacity'] = '0.4'
+        return res
+
     def _get_menu_entries(self):
         """ Method returning menu entries to display on the website view of the
         event, possibly depending on some options in inheriting modules. """