Add a folder-id to item processing

This allows to define a folder when uploading files. All generated
items are associated to this folder on creation.

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

@@ -36,6 +36,7 @@ object ProcessItemArgs {
       language: Language,
       direction: Option[Direction],
       sourceAbbrev: String,
+      folderId: Option[Ident],
       validFileTypes: Seq[MimeType]
   )
 

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

@@ -27,7 +27,9 @@ case class ScanMailboxArgs(
     // delete the after submitting (only if targetFolder is None)
     deleteMail: Boolean,
     // set the direction when submitting
-    direction: Option[Direction]
+    direction: Option[Direction],
+    // set a folder for items
+    itemFolder: Option[Ident]
 )
 
 object ScanMailboxArgs {