Add new way for uploading files to any collective

Applications running next to docspell may want a way to upload files
to any collective for integration purposes. This endpoint can be used
for this. It is disabled by default and can be enabled via the
configuration file.

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

@@ -40,6 +40,9 @@ object Implicits {
   implicit val caleventReader: ConfigReader[CalEvent] =
     ConfigReader[String].emap(reason(CalEvent.parse))
 
+  implicit val priorityReader: ConfigReader[Priority] =
+    ConfigReader[String].emap(reason(Priority.fromString))
+
   def reason[A: ClassTag](
       f: String => Either[String, A]
   ): String => Either[FailureReason, A] =