docs: add comments

Author: Flash0ver

src/Sentry/Internal/StructuredLogBatchBuffer.cs

@@ -8,6 +8,8 @@ namespace Sentry.Internal;
 /// <remarks>
 /// Must be attempted to flush via <see cref="TryEnterFlushScope"/> when either the <see cref="Capacity"/> is reached,
 /// or when the <see cref="_timeout"/> is exceeded.
+/// Utilizes a <see cref="ScopedCountdownLock"/>, basically used as an inverse <see cref="ReaderWriterLockSlim"/>,
+/// allowing multiple threads for <see cref="Add"/> or exclusive access for <see cref="FlushScope.Flush()"/>.
 /// </remarks>
 [DebuggerDisplay("Name = {Name}, Capacity = {Capacity}, Additions = {_additions}, AddCount = {AddCount}, IsDisposed = {_disposed}")]
 internal sealed class StructuredLogBatchBuffer : IDisposable

test/Sentry.Tests/Threading/ScopedCountdownLockTests.cs

@@ -88,6 +88,9 @@ public void TryEnterLockScope_IsEngaged_IsSet()
         counterTwo.Dispose();
         AssertEngaged(false, 1);
 
+        // would block if the timeout was infinite because the engaged lock is not yet set
+        lockOne.Wait(TimeSpan.Zero);
+
         // exit last CounterScope ... count of engaged lock reaches zero ... sets the lock
         counterOne.Dispose();
         AssertEngaged(true, 0);