Properly initialize thread pools

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

@@ -2,6 +2,8 @@ package docspell.common
 
 import java.util.concurrent.atomic.AtomicLong
 import java.util.concurrent.{Executors, ThreadFactory}
+import cats.effect._
+import scala.concurrent._
 
 object ThreadFactories {
 
@@ -17,4 +19,16 @@ object ThreadFactories {
       }
     }
 
+  def executorResource[F[_]: Sync](
+      c: => ExecutionContextExecutorService
+  ): Resource[F, ExecutionContextExecutorService] =
+    Resource.make(Sync[F].delay(c))(ec => Sync[F].delay(ec.shutdown))
+
+  def cached[F[_]: Sync](tf: ThreadFactory): Resource[F, ExecutionContextExecutorService] =
+    executorResource(
+      ExecutionContext.fromExecutorService(Executors.newCachedThreadPool(tf))
+    )
+
+  def fixed[F[_]: Sync](n: Int, tf: ThreadFactory): Resource[F, ExecutionContextExecutorService] =
+    executorResource(ExecutionContext.fromExecutorService(Executors.newFixedThreadPool(n, tf)))
 }