[FIX] website_mass_mailing, *: fix display of backend popup edition

In the backend, when a mailing popup was being edited, it was not
centered in the edition area (and went under the editor UI) and was not
using the correct style.

task-2083465

closes odoo/odoo#38421

Signed-off-by: Quentin Smetz (qsm) <qsm@odoo.com>

addons/web_editor/static/src/scss/wysiwyg.scss

@@ -429,3 +429,19 @@ img.o_we_custom_image.mx-auto {
         }
     }
 }
+
+// User modal in edit mode
+.editor_enable, .note-editable {
+    .modal:not(.o_technical_modal) {
+        top: 40px;
+        right: 0;
+        bottom: 0;
+        left: $o-we-sidebar-width;
+        width: auto;
+        height: auto;
+
+        .modal-dialog {
+            padding: 0.5rem 0; // To use more editor space if necessary
+        }
+    }
+}

addons/website/static/src/scss/website.edit_mode.scss

@@ -136,19 +136,3 @@ table.editorbar-panel {
         cursor: pointer;
     }
 }
-
-// User modal in edit mode
-.editor_enable, .note-editable {
-    .modal:not(.o_technical_modal) {
-        top: 40px;
-        right: 0;
-        bottom: 0;
-        left: $o-we-sidebar-width;
-        width: auto;
-        height: auto;
-
-        .modal-dialog {
-            padding: 0.5rem 0; // To use more editor space if necessary
-        }
-    }
-}

addons/website_mass_mailing/static/src/xml/website_mass_mailing.xml

@@ -4,10 +4,10 @@
     <div class="modal fade show d-block o_newsletter_modal">
         <div role="dialog" class="modal-dialog modal-dialog-centered">
             <div class="modal-content">
-                <header>
+                <header class="modal-header">
                     <button type="button" class="close" aria-label="Close" tabindex="-1">×</button>
                 </header>
-                <div id="wrapper" class="modal-body oe_structure"></div>
+                <div id="wrapper" class="modal-body p-0 oe_structure oe_empty"></div>
             </div>
         </div>
     </div>