Add validate_input decorator

[harell]

• [ ] see assert$input_type
• [ ] write good detail section in function documentation
• [ ] add example of NA from a different source
• [ ] add example when the default input is not NA

Car <- function(model = NA_character_, hp = NA_real_) return(
   data.frame(modek = model, hp = hp)
)

Car <- validate_input (Car)
car <- Car(model = 555, hp = 120) # fails because model is numeric rather than character 

[harell]

validate_input decorator