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/leakdetector/LeakGPIODetector.cpp b/src/leakdetector/LeakGPIODetector.cpp
new file mode 100644
index 0000000..f21d1b5
--- /dev/null
+++ b/src/leakdetector/LeakGPIODetector.cpp
@@ -0,0 +1,89 @@
+#include "LeakGPIODetector.hpp"
+
+#include "LeakEvents.hpp"
+#include "SystemdInterface.hpp"
+
+#include <sdbusplus/async.hpp>
+#include <sdbusplus/message/native_types.hpp>
+
+#include <array>
+#include <functional>
+#include <string>
+#include <string_view>
+#include <utility>
+
+namespace leak
+{
+
+namespace config
+{
+
+/** @brief Leak level to systemd target service map */
+static constexpr std::array<std::pair<config::DetectorLevel, std::string_view>,
+                            2>
+    leakActionTargets = {{{config::DetectorLevel::warning,
+                           "xyz.openbmc_project.leakdetector.warning@"},
+                          {config::DetectorLevel::critical,
+                           "xyz.openbmc_project.leakdetector.critical@"}}};
+
+} // namespace config
+
+static auto getObjectPath(const std::string& detectorName)
+    -> sdbusplus::message::object_path
+{
+    return (
+        sdbusplus::message::object_path(DetectorIntf::namespace_path::value) /
+        DetectorIntf::namespace_path::detector / detectorName);
+}
+
+GPIODetector::GPIODetector(sdbusplus::async::context& ctx, Events& leakEvents,
+                           const config::DetectorConfig& config) :
+    DetectorIntf(ctx, getObjectPath(config.name).str.c_str()), ctx(ctx),
+    leakEvents(leakEvents), config(config),
+    gpioInterface(ctx, config.name, config.pinName,
+                  (config.polarity == config::PinPolarity::activeLow),
+                  std::bind_front(&GPIODetector::updateGPIOStateAsync, this))
+{
+    pretty_name<false>(config.name);
+    type<false>(config.type);
+
+    ctx.spawn(gpioInterface.start());
+
+    debug("Created leak detector {NAME}", "NAME", config.name);
+}
+
+auto GPIODetector::updateGPIOStateAsync(bool gpioState)
+    -> sdbusplus::async::task<>
+{
+    auto newState = gpioState ? DetectorIntf::DetectorState::Abnormal
+                              : DetectorIntf::DetectorState::Normal;
+
+    debug("Updating detector {DETECTOR} state to {STATE}", "DETECTOR",
+          config.name, "STATE", newState);
+
+    if (newState != state_)
+    {
+        state(newState);
+
+        co_await leakEvents.generateLeakEvent(getObjectPath(config.name),
+                                              state_, config.level);
+        if (state_ != DetectorIntf::DetectorState::Normal)
+        {
+            for (const auto& [level, serviceSuffix] : config::leakActionTargets)
+            {
+                if (config.level == level)
+                {
+                    auto target = std::string(serviceSuffix) + config.name +
+                                  ".service";
+                    debug("Starting systemd target {TARGET}", "TARGET", target);
+                    co_await systemd::SystemdInterface::startUnit(ctx, target);
+                    break;
+                }
+            }
+        }
+    }
+
+    co_return;
+}
+
+} // namespace leak