[FSSDK-9526] refact: Implements a warning log for polling interval less than 30s

OptimizelySDK.Tests/ConfigTest/PollingProjectConfigManagerTest.cs

@@ -139,6 +139,25 @@ public void TestTimedoutOnlyIfSchedulerStarted()
             configManager.Dispose();
         }
 
+        [Test]
+        public void TestWarnLogIfPollingTimeIsLessThanThirty()
+        {
+            var below30Seconds = TimeSpan.FromSeconds(29);
+            _ = new TestPollingProjectConfigManager(below30Seconds,
+                TimeSpan.FromSeconds(10), true, LoggerMock.Object, new int[] { });
+            LoggerMock.Verify(l => l.Log(LogLevel.WARN,
+                "Polling intervals below 30 seconds are not recommended."), Times.Once);
+        }
+        [Test]
+        public void TestWarnLogNotTriggeredIfPollingTimeIsGreaterThanThirty()
+        {
+            var above30Seconds = TimeSpan.FromMinutes(1);
+            _ = new TestPollingProjectConfigManager(above30Seconds,
+                TimeSpan.FromMilliseconds(10), true, LoggerMock.Object, new int[] { });
+            LoggerMock.Verify(l => l.Log(LogLevel.WARN,
+                "Polling intervals below 30 seconds are not recommended."), Times.Never);
+        }
+
         [Test]
         public void TestDontTimedoutIfSchedulerNotStarted()
         {

OptimizelySDK/Config/PollingProjectConfigManager.cs

@@ -65,6 +65,10 @@ public PollingProjectConfigManager(TimeSpan period, TimeSpan blockingTimeout,
             Logger = logger;
             ErrorHandler = errorHandler;
             BlockingTimeout = blockingTimeout;
+            if (period.TotalSeconds < 30)
+            {
+                Logger?.Log(LogLevel.WARN, "Polling intervals below 30 seconds are not recommended.");
+            }
             PollingInterval = period;
             AutoUpdate = autoUpdate;