Integrate periodic tasks

The first use case for periodic task is the cleanup of expired
invitation keys. This is part of a house-keeping periodic task.

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

@@ -16,6 +16,9 @@ case class Timestamp(value: Instant) {
   def minus(d: Duration): Timestamp =
     Timestamp(value.minusNanos(d.nanos))
 
+  def - (d: Duration): Timestamp =
+    minus(d)
+
   def minusHours(n: Long): Timestamp =
     Timestamp(value.minusSeconds(n * 60 * 60))
 
@@ -31,6 +34,9 @@ case class Timestamp(value: Instant) {
   def atUTC: ZonedDateTime = atZone(Timestamp.UTC)
 
   def asString: String = value.toString
+
+  def < (other: Timestamp): Boolean =
+    this.value.isBefore(other.value)
 }
 
 object Timestamp {

modules/common/src/main/scala/docspell/common/pureconfig/Implicits.scala

@@ -4,6 +4,7 @@ import docspell.common._
 import _root_.pureconfig._
 import _root_.pureconfig.error.{CannotConvert, FailureReason}
 import scodec.bits.ByteVector
+import com.github.eikek.calev.CalEvent
 
 import scala.reflect.ClassTag
 
@@ -31,6 +32,10 @@ object Implicits {
       else ByteVector.encodeUtf8(str).left.map(ex => s"Invalid utf8 string: ${ex.getMessage}")
     })
 
+  implicit val caleventReader: ConfigReader[CalEvent] =
+    ConfigReader[String].emap(reason(CalEvent.parse))
+
+
   def reason[A: ClassTag](f: String => Either[String, A]): String => Either[FailureReason, A] =
     in =>
       f(in).left.map(str => CannotConvert(in, implicitly[ClassTag[A]].runtimeClass.toString, str))