Taylor Swift isn't taking any chances when it comes to keeping details of her wedding to Travis Kelce under wraps ... 'cause TMZ has learned guests are required to sign a strict non-disclosure agreement before receiving information about the highly anticipated event. Sources with direct knowledge tell TMZ ... family and friends who received coveted invitations were also sent an iron-clad NDA. As TMZ first reported ... Taylor called up guests last month to personally invite them to the wedding,