Deprecate multiple path route mapping

Drawing routes with multiple paths complicates route drawing enough to
warrant deprecation. Transitioning the routing mapper to use keywords
would result in a 1.25-1.5x improvement in speed, and it would be
substantially easier to do if we drop this feature. Most developers draw
one path per route, so this feature is likely seldom used. Developers
may also leverage with_options or a loop to make drawing easier.

```ruby
get "/users", "/other_path", to: "users#index"

get "/users", to: "users#index"
get "/other_path", to: "users#index"
```

Author: gmcgibbon

actionpack/CHANGELOG.md

@@ -1,3 +1,17 @@
+*   Deprecate drawing routes with multiple paths to make routing faster.
+    You may use `with_options` or a loop to make drawing multiple paths easier.
+
+    ```ruby
+    # Before
+    get "/users", "/other_path", to: "users#index"
+
+    # After
+    get "/users", to: "users#index"
+    get "/other_path", to: "users#index"
+    ```
+
+    *Gannon McGibbon*
+
 *   Make `http_cache_forever` use `immutable: true`
 
     *Nate Matykiewicz*

actionpack/lib/action_dispatch/routing/mapper.rb

@@ -1935,6 +1935,11 @@ def path_scope(path)
           end
 
           def map_match(paths, options)
+            ActionDispatch.deprecator.warn(<<-MSG.squish) if paths.count > 1
+              Mapping a route with multiple paths is deprecated and
+              will be removed in Rails 8.1. Please use multiple method calls instead.
+            MSG
+
             if (on = options[:on]) && !VALID_ON_OPTIONS.include?(on)
               raise ArgumentError, "Unknown scope #{on.inspect} given to :on"
             end

actionpack/test/dispatch/routing_test.rb

@@ -763,7 +763,8 @@ def test_projects_people
 
           member do
             put  :accessible_projects
-            post :resend, :generate_new_password
+            post :resend
+            post :generate_new_password
           end
         end
       end
@@ -812,7 +813,8 @@ def test_projects_posts
     draw do
       resources :projects do
         resources :posts do
-          get  :archive, :toggle_view, on: :collection
+          get :archive, on: :collection
+          get :toggle_view, on: :collection
           post :preview, on: :member
 
           resource :subscription
@@ -1533,8 +1535,10 @@ def test_index
   end
 
   def test_match_with_many_paths_containing_a_slash
-    draw do
-      get "get/first", "get/second", "get/third", to: "get#show"
+    assert_deprecated(ActionDispatch.deprecator) do
+      draw do
+        get "get/first", "get/second", "get/third", to: "get#show"
+      end
     end
 
     get "/get/first"
@@ -1570,9 +1574,11 @@ def test_match_shorthand_inside_namespace
   end
 
   def test_match_shorthand_with_multiple_paths_inside_namespace
-    draw do
-      namespace :proposals do
-        put "activate", "inactivate"
+    assert_deprecated(ActionDispatch.deprecator) do
+      draw do
+        namespace :proposals do
+          put "activate", "inactivate"
+        end
       end
     end