fix: harden task recovery and DR contract handling

ros2/bt_executor/tools/test_recovery_policy.cpp

@@ -0,0 +1,16 @@
+#include <bt_executor/recovery_policy.hpp>
+#include <cassert>
+#include <string>
+int main() {
+  using namespace bt_executor;
+  assert(!recovery_authorized("", ""));
+  assert(!recovery_authorized("short", "short"));
+  assert(recovery_authorized("sixteen-byte-key!", "sixteen-byte-key!"));
+  assert(!recovery_authorized("sixteen-byte-key!", "sixteen-byte-key?"));
+  assert(!recovery_authorized("sixteen-byte-key!", "sixteen-byte-key!x"));
+  assert(!recovery_authorized(std::string(1025,'x'),std::string(1025,'x')));
+  assert(!recovery_resume_permitted(false,false,false));
+  assert(!recovery_resume_permitted(true,true,false));
+  assert(recovery_resume_permitted(true,false,false));
+  assert(recovery_resume_permitted(false,true,true));
+}