Coupon - Write custom messages + Case sensitive off option

Coupon has an issue. Some clients say that the coupon is not working.

Mostly it's because it is case sensitive. (maybe make an option to set it to case-senstive or not, so admin can still choose)

But no message is shown that the coupon is not working or is wrong or expired.

Maybe add logic fields for this for different situations where we can set our own sentence that we wish to become visible.

Case 1 - Coupon is expired - users fill in -message: Sorry the coupon has expired.
Case 2 - wrong coupon filled in - message: Sorry, it seems this coupon doesn't exist.
Case 3 - Coupon limited reached - message: Sorry, you're too late the maximum use of this coupon has been used.

thank you.