Create a model hook around the lockable warden hook to reset attempts

Resetting failed attempts after sign in happened inside a warden hook
specific for the lockable module, but that was hidden inside the hook
implementation and didn't allow any user customization.

One such customization needed for example is to direct these updates to
a write DB when using a multi-DB setup. With the logic hidden in the
warden hook this wasn't possible, now that it's exposed in a model
method much like trackable, we can override the model method to wrap it
in a connection switch block for example, point to a write DB, and
simply call `super`.

Closes #5310
Related to #5264 and #5133

lib/devise/hooks/lockable.rb

@@ -3,10 +3,7 @@
 # After each sign in, if resource responds to failed_attempts, sets it to 0
 # This is only triggered when the user is explicitly set (with set_user)
 Warden::Manager.after_set_user except: :fetch do |record, warden, options|
-  if record.respond_to?(:failed_attempts) && warden.authenticated?(options[:scope])
-    unless record.failed_attempts.to_i.zero?
-      record.failed_attempts = 0
-      record.save(validate: false)
-    end
+  if record.respond_to?(:reset_failed_attempts!) && warden.authenticated?(options[:scope])
+    record.reset_failed_attempts!
   end
 end

lib/devise/models/lockable.rb

@@ -57,6 +57,14 @@ def unlock_access!
         save(validate: false)
       end
 
+      # Resets failed attempts counter to 0.
+      def reset_failed_attempts!
+        if respond_to?(:failed_attempts) && !failed_attempts.to_i.zero?
+          self.failed_attempts = 0
+          save(validate: false)
+        end
+      end
+
       # Verifies whether a user is locked or not.
       def access_locked?
         !!locked_at && !lock_expired?
@@ -110,7 +118,7 @@ def valid_for_authentication?
           false
         end
       end
-      
+
       def increment_failed_attempts
         self.class.increment_counter(:failed_attempts, id)
         reload