Extract the deprecation message to avoid duplication

lib/simple_form.rb

@@ -24,6 +24,16 @@ module SimpleForm
     SimpleForm::Components.eager_load!
   end
 
+  CUSTOM_INPUT_DEPRECATION_WARN = <<-WARN
+%{name} method now accepts a `context` argument. The method definition without the argument is deprecated and will be removed in the next Simple Form version. Change your code from:
+
+    def %{name}
+
+to
+
+    def %{name}(context)
+  WARN
+
   ## CONFIGURATION OPTIONS
 
   # Method used to tidy up errors.

lib/simple_form/components/label_input.rb

@@ -1,16 +1,6 @@
 module SimpleForm
   module Components
     module LabelInput
-      DEPRECATION_WARN = <<-WARN
-%{name} method now accepts a `context` argument. The method definition without the argument is deprecated and will be removed in the next Simple Form version. Change your code from:
-
-    def %{name}
-
-to
-
-    def %{name}(context)
-      WARN
-
       extend ActiveSupport::Concern
 
       included do
@@ -27,7 +17,7 @@ to
         method = method(:input)
 
         if method.arity == 0
-          ActiveSupport::Deprecation.warn(DEPRECATION_WARN % { name: 'input' })
+          ActiveSupport::Deprecation.warn(SimpleForm::CUSTOM_INPUT_DEPRECATION_WARN % { name: 'input' })
 
           method.call
         else
@@ -39,7 +29,7 @@ to
         method = method(:label)
 
         if method.arity == 0
-          ActiveSupport::Deprecation.warn(DEPRECATION_WARN % { name: 'label' })
+          ActiveSupport::Deprecation.warn(SimpleForm::CUSTOM_INPUT_DEPRECATION_WARN % { name: 'label' })
 
           method.call
         else

lib/simple_form/wrappers/leaf.rb

@@ -1,16 +1,6 @@
 module SimpleForm
   module Wrappers
     class Leaf
-      DEPRECATION_WARN = <<-WARN
-%{name} method now accepts a `context` argument. The method definition without the argument is deprecated and will be removed in the next Simple Form version. Change your code from:
-
-    def %{name}
-
-to
-
-    def %{name}(context)
-      WARN
-
       attr_reader :namespace, :options
 
       def initialize(namespace, options={})
@@ -22,7 +12,7 @@ to
         method = input.method(@namespace)
 
         if method.arity == 0
-          ActiveSupport::Deprecation.warn(DEPRECATION_WARN % { name: @namespace })
+          ActiveSupport::Deprecation.warn(SimpleForm::CUSTOM_INPUT_DEPRECATION_WARN % { name: @namespace })
 
           method.call
         else