an error in your SQL syntax; check the manual that corresponds to your MySQL server version
Your CREATE TABLE will fail because there is no PIN column mentioned in KEY `idxPIN` (`PIN`) line.
MySQL 5.6 does not allow an expression as default value. Use trigger:
CREATE TABLE `Customer` (
  `ID` bigint(20) NOT NULL AUTO_INCREMENT,
  `Version` bigint(20) DEFAULT 0,
  `FirstName` varchar(100) COLLATE utf8mb4_unicode_ci NOT NULL,
  `LastName` varchar(100) COLLATE utf8mb4_unicode_ci NOT NULL,
  `UserName` varchar(100) COLLATE utf8mb4_unicode_ci NOT NULL,
  `Password` varchar(64) COLLATE utf8mb4_unicode_ci DEFAULT NULL,
  `PasswordSalt` varchar(64) COLLATE utf8mb4_unicode_ci DEFAULT NULL,
  `PasswordExpires` datetime DEFAULT NULL,
  `ForcePasswordChange` bit(1) DEFAULT b'0',
  `Email` varchar(100) COLLATE utf8mb4_unicode_ci DEFAULT NULL,
  `Phone` varchar(15) COLLATE utf8mb4_unicode_ci DEFAULT NULL,
  `NickName` varchar(50) COLLATE utf8mb4_unicode_ci DEFAULT NULL,
  `TextNumber` varchar(15) COLLATE utf8mb4_unicode_ci DEFAULT NULL,
  `IsValid` bit(1) DEFAULT b'0',
  `IsMigrated` bit(1) DEFAULT b'1',
  `UUID` varchar(64) COLLATE utf8mb4_unicode_ci DEFAULT NULL,
  `InsertTs` timestamp NOT NULL DEFAULT current_timestamp(),
  `UpdateTs` timestamp NOT NULL DEFAULT current_timestamp() ON UPDATE current_timestamp(),
  PRIMARY KEY (`ID`),
  UNIQUE KEY `uk_User_UserName_UNIQUE` (`UserName`),
  UNIQUE KEY `uk_User_UUID_UNIQUE` (`UUID`),
-- -------------
`PIN` INT,
-- -------------
  KEY `idxPIN` (`PIN`)
) ENGINE=InnoDB AUTO_INCREMENT=90184 DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_unicode_ci;

CREATE TRIGGER set_uuid
BEFORE INSERT 
ON Customer
FOR EACH ROW
SET NEW.UUID = COALESCE(NEW.UUID, sha2(uuid(),256));