public ShenYuTestCaseSpecBuilder addExists(final Method method, final String endpoint, final Map<String, ?> body) {
            return add(exists(method, endpoint, body));
        }
add exist method endpoint case spec.
@param method method
@param endpoint endpoint
@param body body
@return ShenYuTestCaseSpecBuilder
shenyu-e2e/shenyu-e2e-engine/src/main/java/org/apache/shenyu/e2e/engine/scenario/specification/ShenYuCaseSpec.java