[FIX] website: fix scroll table of content

This commit fixes two bugs with the table of content snippet:

- Before this commit, the scrollspy position for the table of content
navbar was incorrect in fullscreen or edit mode due to the calculation
being based on the presence of the main navbar, which is not present in
those modes.

- Before this commit, when the table of content navbar contained enough
elements to exceed the height of the page, the bottom elements were not
accessible without first scrolling through the entire table of content.
This commit addresses this issue by adding a scrollbar to the navbar,
allowing for easier access to these links.

opw-3115597

closes odoo/odoo#109927

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

addons/website/static/src/snippets/s_table_of_content/000.js

@@ -23,7 +23,7 @@ const TableOfContent = publicWidget.Widget.extend({
      */
     destroy() {
         this.$target.css('top', '');
-        this.$target.find('.s_table_of_content_navbar').css('top', '');
+        this.$target.find('.s_table_of_content_navbar').css({top: '', maxHeight: ''});
         this._super(...arguments);
     },
 
@@ -42,8 +42,10 @@ const TableOfContent = publicWidget.Widget.extend({
         this.$target.css('top', isHorizontalNavbar ? position : '');
         this.$target.find('.s_table_of_content_navbar').css('top', isHorizontalNavbar ? '' : position + 20);
         const $mainNavBar = $('#oe_main_menu_navbar');
-        position += $mainNavBar.length ? $mainNavBar.outerHeight() : 0;
+        const mainNavBarHidden = document.body.classList.contains('o_fullscreen') || this.editableMode;
+        position += !mainNavBarHidden && $mainNavBar.length ? $mainNavBar.outerHeight() : 0;
         position += isHorizontalNavbar ? this.$target.outerHeight() : 0;
+        this.$target.find('.s_table_of_content_navbar').css('maxHeight', isHorizontalNavbar ? '' : `calc(100vh - ${position + 40}px)`);
         if (this.previousPosition !== position) {
             // The scrollSpy must be destroyed before calling it again.
             // Otherwise the call has no effect.

addons/website/static/src/snippets/s_table_of_content/000.scss

@@ -4,6 +4,9 @@
             &.s_table_of_content_horizontal_navbar, &.s_table_of_content_vertical_navbar .s_table_of_content_navbar {
                 @include o-position-sticky($top: 0px);
             }
+            &.s_table_of_content_vertical_navbar .s_table_of_content_navbar {
+                overflow: auto;
+            }
         }
         &:not(.s_table_of_content_navbar_sticky) {
             &, .s_table_of_content_navbar {