[FIX] website_profile,forum: avoid relative links

The origin parameter must be an absolute link (starting with a /)
To be consistent and always have a leading slash (and avoid relative
links if the developer forgot to add a leading slash)

addons/website_forum/views/website_forum_profile.xml

@@ -12,7 +12,7 @@
     <template id="user_profile_sub_nav" inherit_id="website_profile.user_profile_sub_nav">
         <xpath expr="//nav" position="before">
             <div t-if="request.params.get('forum_origin')" class="o_wprofile_all_users_nav_btn_container col pr-0 flex-grow-0">
-                <a t-att-href="(request.website.domain or '') + request.params.get('forum_origin')"
+                <a t-att-href="(request.website.domain or '') + '/' + request.params.get('forum_origin').lstrip('/')"
                     class="o_wprofile_all_users_nav_btn btn text-nowrap">
                     <i class="fa fa-chevron-left small"/> Back
                 </a>

addons/website_profile/views/website_profile.xml

@@ -394,7 +394,7 @@
                 <nav t-if="request.params.get('url_origin') and request.params.get('name_origin')" aria-label="breadcrumb">
                     <ol class="breadcrumb p-0 bg-white">
                         <li class="breadcrumb-item">
-                            <a t-att-href="(request.website.domain or '') + request.params.get('url_origin')" t-esc="request.params.get('name_origin')"/>
+                            <a t-att-href="(request.website.domain or '') + '/' + request.params.get('url_origin').lstrip('/')" t-esc="request.params.get('name_origin')"/>
                         </li>
                         <li class="breadcrumb-item">Badges</li>
                     </ol>