Errors details should be return in endpoint for for file process with FileOutputProcessor

[inkhey]

actually: get_validation_error return empty dict for details of error in FileOutputProcessor. That's mean using file output decorator, there is no explicit error when output validation failed. Explicit errors message about file output already exist in validate method.

todo: Code need to be refactored in order to have error detail in both validate and get_validation_error methods. That's mean we can have explicit error detail from endpoint result.