Create tasks to generate all previews

There is a task to generate preview images per attachment. It can
either add them (if not present yet) or overwrite them (e.g. some
config has changed).

There is a task that selects all attachments without previews and
submits a task to create it. This is submitted on start automatically
to generate previews for all existing attachments.

modules/store/src/main/scala/docspell/store/queries/QAttachment.scala

@@ -17,6 +17,22 @@ import doobie.implicits._
 object QAttachment {
   private[this] val logger = org.log4s.getLogger
 
+  def deletePreview[F[_]: Sync](store: Store[F])(attachId: Ident): F[Int] = {
+    val findPreview =
+      for {
+        rp <- RAttachmentPreview.findById(attachId)
+      } yield rp.toSeq
+
+    Stream
+      .evalSeq(store.transact(findPreview))
+      .map(_.fileId.id)
+      .flatMap(store.bitpeace.delete)
+      .map(flag => if (flag) 1 else 0)
+      .evalMap(_ => store.transact(RAttachmentPreview.delete(attachId)))
+      .compile
+      .foldMonoid
+  }
+
   /** Deletes an attachment, its related source and meta data records.
     * It will only delete an related archive file, if this is the last
     * attachment in that archive.

modules/store/src/main/scala/docspell/store/records/RAttachment.scala

@@ -231,6 +231,38 @@ object RAttachment {
   def findItemId(attachId: Ident): ConnectionIO[Option[Ident]] =
     selectSimple(Seq(itemId), table, id.is(attachId)).query[Ident].option
 
+  def findWithoutPreview(
+      coll: Option[Ident],
+      chunkSize: Int
+  ): Stream[ConnectionIO, RAttachment] = {
+    val aId   = Columns.id.prefix("a")
+    val aItem = Columns.itemId.prefix("a")
+    val pId   = RAttachmentPreview.Columns.id.prefix("p")
+    val iId   = RItem.Columns.id.prefix("i")
+    val iColl = RItem.Columns.cid.prefix("i")
+
+    val cols = all.map(_.prefix("a"))
+    val baseJoin =
+      table ++ fr"a LEFT OUTER JOIN" ++
+        RAttachmentPreview.table ++ fr"p ON" ++ pId.is(aId)
+
+    val baseCond =
+      Seq(pId.isNull)
+
+    coll match {
+      case Some(cid) =>
+        val join = baseJoin ++ fr"INNER JOIN" ++ RItem.table ++ fr"i ON" ++ iId.is(aItem)
+        val cond = and(baseCond ++ Seq(iColl.is(cid)))
+        selectSimple(cols, join, cond)
+          .query[RAttachment]
+          .streamWithChunkSize(chunkSize)
+      case None =>
+        selectSimple(cols, baseJoin, and(baseCond))
+          .query[RAttachment]
+          .streamWithChunkSize(chunkSize)
+    }
+  }
+
   def findNonConvertedPdf(
       coll: Option[Ident],
       chunkSize: Int