control: Store/use trigger enable functions on events

Create and store trigger enablement functions on the events based on the
trigger's configuration so that they can be enabled separately from when
the event is created. This will allow actions that load events to be
able to be parsed and then enabled when the action determines that the
events should be enabled. It also supports the use of SIGHUP to reload
the event configuration since the events JSON configuration must
successfully be loaded before the newly created events can be enabled in
place of the currently enabled events.

Change-Id: I31871ee1691d5e6b26fe16cde2a829c426ad6504
Signed-off-by: Matthew Barth <msbarth@us.ibm.com>
diff --git a/control/json/triggers/trigger_aliases.hpp b/control/json/triggers/trigger_aliases.hpp
new file mode 100644
index 0000000..c390864
--- /dev/null
+++ b/control/json/triggers/trigger_aliases.hpp
@@ -0,0 +1,41 @@
+/**
+ * Copyright © 2021 IBM Corporation
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+#pragma once
+
+#include "action.hpp"
+#include "manager.hpp"
+
+#include <nlohmann/json.hpp>
+
+#include <functional>
+#include <memory>
+#include <vector>
+
+namespace phosphor::fan::control::json::trigger
+{
+
+using json = nlohmann::json;
+
+// Trigger enablement function
+using enableTrigger = std::function<void(
+    const std::string&, Manager*, std::vector<std::unique_ptr<ActionBase>>&)>;
+
+// Trigger creation function
+using createTrigger =
+    std::function<enableTrigger(const json&, const std::string&, Manager*,
+                                std::vector<std::unique_ptr<ActionBase>>&)>;
+
+} // namespace phosphor::fan::control::json::trigger