Fix broken Members link when relative URL root paths are used

Navigating to the "Members" section of a project would omit the
relative URL root path. Fix the redirection and eliminate the
need for a redirection in the first place.

Related Rails issue discussing omitting the leading slash in the
redirect paths: https://github.com/rails/rails/issues/21193

Fix other redirections failing to work with relative roots.

app/views/layouts/nav/sidebar/_project.html.haml

@@ -290,7 +290,7 @@
               Members
           %ul.sidebar-sub-level-items.is-fly-out-only
             = nav_link(path: %w[members#show], html_options: { class: "fly-out-top-item" } ) do
-              = link_to project_settings_members_path(@project) do
+              = link_to project_project_members_path(@project) do
                 %strong.fly-out-top-item-name
                   #{ _('Members') }
 

config/routes/ci.rb

 namespace :ci do
   resource :lint, only: [:show, :create]
 
-  root to: redirect('/')
+  root to: redirect('')
 end

config/routes/project.rb

@@ -443,7 +443,7 @@ constraints(ProjectUrlConstrainer.new) do
       ## EE-specific
 
       namespace :settings do
-        get :members, to: redirect('/%{namespace_id}/%{project_id}/project_members')
+        get :members, to: redirect("%{namespace_id}/%{project_id}/project_members")
         resource :ci_cd, only: [:show], controller: 'ci_cd'
         resource :integrations, only: [:show]
 

config/routes/snippets.rb

@@ -17,5 +17,5 @@ resources :snippets, concerns: :awardable do
   end
 end
 
-get '/s/:username', to: redirect('/u/%{username}/snippets'),
+get '/s/:username', to: redirect('u/%{username}/snippets'),
                     constraints: { username: /[a-zA-Z.0-9_\-]+(?<!\.atom)/ }

config/routes/user.rb

@@ -32,17 +32,17 @@ scope(constraints: { username: Gitlab::PathRegex.root_namespace_route_regex }) d
     get :snippets
     get :exists
     get :pipelines_quota
-    get '/', to: redirect('/%{username}'), as: nil
+    get '/', to: redirect('%{username}'), as: nil
   end
 
   # Compatibility with old routing
   # TODO (dzaporozhets): remove in 10.0
-  get '/u/:username', to: redirect('/%{username}')
+  get '/u/:username', to: redirect('%{username}')
   # TODO (dzaporozhets): remove in 9.0
-  get '/u/:username/groups', to: redirect('/users/%{username}/groups')
-  get '/u/:username/projects', to: redirect('/users/%{username}/projects')
-  get '/u/:username/snippets', to: redirect('/users/%{username}/snippets')
-  get '/u/:username/contributed', to: redirect('/users/%{username}/contributed')
+  get '/u/:username/groups', to: redirect('users/%{username}/groups')
+  get '/u/:username/projects', to: redirect('users/%{username}/projects')
+  get '/u/:username/snippets', to: redirect('users/%{username}/snippets')
+  get '/u/:username/contributed', to: redirect('users/%{username}/contributed')
 end
 
 constraints(UserUrlConstrainer.new) do