Added Java API and discoverable factory methods for Offset akka#21788

akka-persistence-query/src/main/scala/akka/persistence/query/Offset.scala

@@ -6,6 +6,15 @@ package akka.persistence.query
 
 import java.util.UUID
 
+object Offset {
+
+  // factories to aid discoverability
+  def noOffset: Offset = NoOffset
+  def sequence(value: Long): Offset = Sequence(value)
+  def timeBasedUUID(uuid: UUID): Offset = TimeBasedUUID(uuid)
+
+}
+
 trait Offset
 
 final case class Sequence(val value: Long) extends Offset with Ordered[Sequence] {
@@ -20,4 +29,9 @@ final case class TimeBasedUUID(val value: UUID) extends Offset with Ordered[Time
   override def compare(other: TimeBasedUUID): Int = value.compareTo(other.value)
 }
 
-final case object NoOffset extends Offset
+final case object NoOffset extends Offset {
+  /**
+   * Java API:
+   */
+  def getInstance: Offset = this
+}