Previously, ReplacePlaceholders threw PlaceholderResolutionException when a placeholder could not be resolved. Now, unresolved placeholders are replaced with "NULL" instead. All exception references and related tests have been updated to reflect this new behavior. Documentation has also been revised accordingly.
Refactored PlaceholderExtensions, DtoMappingProfile, and InvokeActionTests
to use the ReC.Application.Common.Dto namespace instead of
ReC.Application.Common.Behaviors.Action. Updated using directives and
namespaces to improve code organization for DTO-related logic.
