Add StringContains expression

pkg/expr/exp.go

@@ -26,6 +26,10 @@ func LessOrEqualNumber(f string, n int) string {
 	return fmt.Sprintf("%s <= %d", f, n)
 }
 
+func StringContains(str, substr string) string {
+	return fmt.Sprintf("%s contains '%s'", str, substr)
+}
+
 func InStringArray(s string, arr []string) string {
 	arrStr := "'" + strings.Join(arr, "','") + "'"
 	return fmt.Sprintf("%s in [%s]", s, arrStr)