Use an enum instead of a boolean to differentiate search

It's not very likely to have more modes of search besides normal and
trashed, but got surprised in that way quite often and it's nicer this
way anyways.

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

@@ -0,0 +1,43 @@
+/*
+ * Copyright 2020 Docspell Contributors
+ *
+ * SPDX-License-Identifier: GPL-3.0-or-later
+ */
+
+package docspell.common
+
+import cats.data.NonEmptyList
+
+import io.circe.Decoder
+import io.circe.Encoder
+
+sealed trait SearchMode { self: Product =>
+
+  final def name: String =
+    productPrefix.toLowerCase
+
+}
+
+object SearchMode {
+
+  final case object Normal  extends SearchMode
+  final case object Trashed extends SearchMode
+
+  def fromString(str: String): Either[String, SearchMode] =
+    str.toLowerCase match {
+      case "normal"  => Right(Normal)
+      case "trashed" => Right(Trashed)
+      case _         => Left(s"Invalid search mode: $str")
+    }
+
+  val all: NonEmptyList[SearchMode] =
+    NonEmptyList.of(Normal, Trashed)
+
+  def unsafe(str: String): SearchMode =
+    fromString(str).fold(sys.error, identity)
+
+  implicit val jsonDecoder: Decoder[SearchMode] =
+    Decoder.decodeString.emap(fromString)
+  implicit val jsonEncoder: Encoder[SearchMode] =
+    Encoder.encodeString.contramap(_.name)
+}