If you want to know if you were one of the 143 million people whose data was breached in a hack of Equifax’s data, the company has a website you can use to find out — but there appears to be a catch: To check, you have to agree to give up your legal right to sue the company for damages. The outrage that clause has now generated could complicate the company’s efforts — backed by Republican lawmakers — to block an imminent rule that would ban companies from forcing customers to agree to such provisions.