fixed translation of Publisher<Void> to Task[Unit]

Author: Roman Janusz

commons-mongo/jvm/src/main/scala/com/avsystem/commons/mongo/typed/TypedClientSession.scala

@@ -25,10 +25,10 @@ class TypedClientSession(val nativeSession: ClientSession)
     nativeSession.startTransaction(transactionOptions)
 
   def commitTransaction: Task[Unit] =
-    single(nativeSession.commitTransaction()).void
+    empty(nativeSession.commitTransaction())
 
   def abortTransaction: Task[Unit] =
-    single(nativeSession.abortTransaction()).void
+    empty(nativeSession.abortTransaction())
 
   def inTransaction[T](
     transactionOptions: TransactionOptions = TransactionOptions.builder().build()

commons-mongo/jvm/src/main/scala/com/avsystem/commons/mongo/typed/TypedMongoDatabase.scala

@@ -39,7 +39,7 @@ class TypedMongoDatabase(
   //TODO: `runCommand`
 
   def drop: Task[Unit] =
-    single(optionalizeFirstArg(nativeDatabase.drop(sessionOrNull))).void
+    empty(optionalizeFirstArg(nativeDatabase.drop(sessionOrNull)))
 
   def listCollectionNames: Observable[String] =
     multi(optionalizeFirstArg(nativeDatabase.listCollectionNames(sessionOrNull)))
@@ -54,9 +54,9 @@ class TypedMongoDatabase(
     name: String,
     setupOptions: CreateCollectionOptions => CreateCollectionOptions = identity,
   ): Task[Unit] =
-    single(optionalizeFirstArg(
+    empty(optionalizeFirstArg(
       nativeDatabase.createCollection(sessionOrNull, name, setupOptions(new CreateCollectionOptions))
-    )).void
+    ))
 
   //TODO: `createView`, `watch`, `aggregate`
 }