Add comment about tmp path

Author: finestructure

Sources/DocUploader/DocUploader.swift

@@ -83,6 +83,8 @@ public struct DocUploader: LambdaHandler {
         logger.info("record: \(record)")
 
         try await run {
+            // When Lambdas are run in quick succession they seem to be seeing the same /tmp file system and unzipping can fail with
+            //   lambda handler returned an error: Error Domain=NSCocoaErrorDomain Code=516 "A file with the same name already exists."
             let outputPath = "/tmp/\(UUID())"
             try Foundation.FileManager.default.createDirectory(at: URL(fileURLWithPath: outputPath), withIntermediateDirectories: true)