[FIX] mail: prevent from stretching small image attachment

task-2447939

closes odoo/odoo#65074

Signed-off-by: Alexandre Kühn (aku) <aku@odoo.com>

addons/mail/static/src/components/attachment/attachment.js

@@ -96,7 +96,8 @@ class Attachment extends Component {
         } else {
             size = '160x160';
         }
-        return `background-image:url(/web/image/${this.attachment.id}/${size}/?crop=true);`;
+        // background-size set to override value from `o_image` which makes small image stretched
+        return `background-image:url(/web/image/${this.attachment.id}/${size}/?crop=true); background-size: auto;`;
     }
 
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