Implement notify-due-items task

modules/common/src/main/scala/docspell/common/Duration.scala

@@ -43,6 +43,9 @@ object Duration {
   def hours(n: Long): Duration =
     apply(JDur.ofHours(n))
 
+  def days(n: Long): Duration =
+    apply(JDur.ofDays(n))
+
   def nanos(n: Long): Duration =
     Duration(n)
 

modules/common/src/main/scala/docspell/common/ItemState.scala

@@ -24,6 +24,9 @@ object ItemState {
       case _            => Left(s"Invalid item state: $str")
     }
 
+  val validStates: Seq[ItemState] =
+    Seq(Created, Confirmed)
+
   def unsafe(str: String): ItemState =
     fromString(str).fold(sys.error, identity)
 

modules/common/src/main/scala/docspell/common/Timestamp.scala

@@ -19,6 +19,12 @@ case class Timestamp(value: Instant) {
   def -(d: Duration): Timestamp =
     minus(d)
 
+  def +(d: Duration): Timestamp =
+    plus(d)
+
+  def plus(d: Duration): Timestamp =
+    Timestamp(value.plusNanos(d.nanos))
+
   def minusHours(n: Long): Timestamp =
     Timestamp(value.minusSeconds(n * 60 * 60))
 
@@ -59,4 +65,6 @@ object Timestamp {
   implicit val decodeTimestamp: Decoder[Timestamp] =
     BaseJsonCodecs.decodeInstantEpoch.map(Timestamp(_))
 
+  implicit val ordering: Ordering[Timestamp] =
+    Ordering.by(_.value)
 }