MySQL: Support index_name in FK constraints (#1871)

tests/sqlparser_mysql.rs

@@ -3988,6 +3988,13 @@ fn parse_straight_join() {
         .verified_stmt("SELECT a.*, b.* FROM table_a STRAIGHT_JOIN table_b AS b ON a.b_id = b.id");
 }
 
+#[test]
+fn mysql_foreign_key_with_index_name() {
+    mysql().verified_stmt(
+        "CREATE TABLE orders (customer_id INT, INDEX idx_customer (customer_id), CONSTRAINT fk_customer FOREIGN KEY idx_customer (customer_id) REFERENCES customers(id))",
+    );
+}
+
 #[test]
 fn parse_drop_index() {
     let sql = "DROP INDEX idx_name ON table_name";