Implement Liquid Leak Detector

Implement liquid leak detector based on design
https://gerrit.openbmc.org/c/openbmc/docs/+/73152.

Related PRs:
https://gerrit.openbmc.org/c/openbmc/phosphor-dbus-interfaces/+/73151
https://gerrit.openbmc.org/c/openbmc/phosphor-dbus-interfaces/+/73707
https://gerrit.openbmc.org/c/openbmc/sdbusplus/+/75461
https://gerrit.openbmc.org/c/openbmc/phosphor-dbus-interfaces/+/75999

Tested:
```
>> busctl tree xyz.openbmc_project.LeakDetector
└─ /xyz
  └─ /xyz/openbmc_project
    └─ /xyz/openbmc_project/state
      └─ /xyz/openbmc_project/state/leak
        └─ /xyz/openbmc_project/state/leak/detector
          ├─ /xyz/openbmc_project/state/leak/detector/TrayDetector1
          └─ /xyz/openbmc_project/state/leak/detector/TrayDetector2

>> echo pull-up > /sys/devices/platform/gpio-sim.0/gpiochip2/sim_gpio0/pull

>> curl -k -H "X-Auth-Token: $token" -X GET https://${bmc}/redfish/v1/Systems/system/LogServices/EventLog/Entries
{
  "@odata.id": "/redfish/v1/Systems/system/LogServices/EventLog/Entries",
  "@odata.type": "#LogEntryCollection.LogEntryCollection",
  "Description": "Collection of System Event Log Entries",
  "Members": [
  	...
    {
      "@odata.id": "/redfish/v1/Systems/system/LogServices/EventLog/Entries/2",
      "@odata.type": "#LogEntry.v1_9_0.LogEntry",
      "AdditionalDataURI": "/redfish/v1/Systems/system/LogServices/EventLog/Entries/2/attachment",
      "Created": "2024-05-10T06:40:30.423+00:00",
      "EntryType": "Event",
      "Id": "2",
      "Message": "xyz.openbmc_project.State.Leak.Detector.LeakDetectedWarning",
      "Modified": "2024-05-10T06:40:30.423+00:00",
      "Name": "System Event Log Entry",
      "Resolved": false,
      "Severity": "Warning"
    }
  ],
  "Members@odata.count": 2,
  "Name": "System Event Log Entries"
}

>> echo pull-down > /sys/devices/platform/gpio-sim.0/gpiochip2/sim_gpio0/pull

>> curl -k -H "X-Auth-Token: $token" -X GET https://${bmc}/redfish/v1/Systems/system/LogServices/EventLog/Entries
{
  "@odata.id": "/redfish/v1/Systems/system/LogServices/EventLog/Entries",
  "@odata.type": "#LogEntryCollection.LogEntryCollection",
  "Description": "Collection of System Event Log Entries",
  "Members": [
	...
    {
      "@odata.id": "/redfish/v1/Systems/system/LogServices/EventLog/Entries/2",
      "@odata.type": "#LogEntry.v1_9_0.LogEntry",
      "AdditionalDataURI": "/redfish/v1/Systems/system/LogServices/EventLog/Entries/2/attachment",
      "Created": "2024-05-10T06:40:30.423+00:00",
      "EntryType": "Event",
      "Id": "2",
      "Message": "xyz.openbmc_project.State.Leak.Detector.LeakDetectedWarning",
      "Modified": "2024-05-10T06:42:23.989+00:00",
      "Name": "System Event Log Entry",
      "Resolved": true,
      "Severity": "Warning"
    },
    {
      "@odata.id": "/redfish/v1/Systems/system/LogServices/EventLog/Entries/3",
      "@odata.type": "#LogEntry.v1_9_0.LogEntry",
      "AdditionalDataURI": "/redfish/v1/Systems/system/LogServices/EventLog/Entries/3/attachment",
      "Created": "2024-05-10T06:42:24.024+00:00",
      "EntryType": "Event",
      "Id": "3",
      "Message": "xyz.openbmc_project.State.Leak.Detector.LeakDetectedNormal",
      "Modified": "2024-05-10T06:42:24.024+00:00",
      "Name": "System Event Log Entry",
      "Resolved": false,
      "Severity": "OK"
    }
  ],
  "Members@odata.count": 3,
  "Name": "System Event Log Entries"
}
```

Change-Id: Id6981deb314ca6852c5e31b932b28e601c2f3976
Signed-off-by: Jagpal Singh Gill <paligill@gmail.com>
diff --git a/src/GPIOInterface.hpp b/src/GPIOInterface.hpp
new file mode 100644
index 0000000..b860551
--- /dev/null
+++ b/src/GPIOInterface.hpp
@@ -0,0 +1,42 @@
+#pragma once
+
+#include <gpiod.hpp>
+#include <sdbusplus/async.hpp>
+
+#include <functional>
+#include <memory>
+#include <string>
+
+namespace gpio
+{
+
+class GPIOInterface
+{
+  public:
+    using Callback_t = std::function<sdbusplus::async::task<>(bool)>;
+
+    GPIOInterface() = delete;
+
+    GPIOInterface(sdbusplus::async::context& ctx,
+                  const std::string& consumerName, const std::string& pinName,
+                  bool activeLow, Callback_t updateStateCallback);
+
+    /** @brief Start the GPIO Interface */
+    auto start() -> sdbusplus::async::task<>;
+
+  private:
+    /** @brief Read the gpio state asynchronously */
+    auto readGPIOAsync() -> sdbusplus::async::task<>;
+
+    /** @brief Read the gpio state asynchronously based on gpio event */
+    auto readGPIOAsyncEvent() -> sdbusplus::async::task<>;
+
+    sdbusplus::async::context& ctx;
+    const std::string& pinName;
+    Callback_t updateStateCallback;
+    gpiod::line line;
+    /** File descriptor based async event handler */
+    std::unique_ptr<sdbusplus::async::fdio> fdioInstance;
+};
+
+} // namespace gpio