Create a simple client for joex in its api module

This client can be used within the backend app and later in other
modules. The `OJoex` object is replaced with a better implementation
where the http client is initialized once on app start.

modules/joexapi/src/main/scala/docspell/joexapi/client/JoexClient.scala

@@ -0,0 +1,55 @@
+package docspell.joexapi.client
+
+import cats.implicits._
+import cats.effect._
+import docspell.common.{Ident, LenientUri}
+import org.http4s.{Method, Request, Uri}
+import org.http4s.client.Client
+import org.http4s.client.blaze.BlazeClientBuilder
+import scala.concurrent.ExecutionContext
+
+import org.log4s.getLogger
+
+trait JoexClient[F[_]] {
+
+  def notifyJoex(base: LenientUri): F[Unit]
+
+  def notifyJoexIgnoreErrors(base: LenientUri): F[Unit]
+
+  def cancelJob(base: LenientUri, job: Ident): F[Unit]
+
+}
+
+object JoexClient {
+
+  private[this] val logger = getLogger
+
+  def apply[F[_]: Sync](client: Client[F]): JoexClient[F] =
+    new JoexClient[F] {
+      def notifyJoex(base: LenientUri): F[Unit] = {
+        val notifyUrl = base / "api" / "v1" / "notify"
+        val req = Request[F](Method.POST, uri(notifyUrl))
+        client.expect[String](req).map(_ => ())
+      }
+
+      def notifyJoexIgnoreErrors(base: LenientUri): F[Unit] =
+        notifyJoex(base).attempt.map {
+          case Right(()) => ()
+          case Left(ex) =>
+            logger.warn(s"Notifying Joex instance '${base.asString}' failed: ${ex.getMessage}")
+            ()
+        }
+
+      def cancelJob(base: LenientUri, job: Ident): F[Unit] = {
+        val cancelUrl = base / "api" / "v1" / "job" / job.id / "cancel"
+        val req = Request[F](Method.POST, uri(cancelUrl))
+        client.expect[String](req).map(_ => ())
+      }
+
+      private def uri(u: LenientUri): Uri =
+        Uri.unsafeFromString(u.asString)
+    }
+
+  def resource[F[_]: ConcurrentEffect](ec: ExecutionContext): Resource[F, JoexClient[F]] =
+    BlazeClientBuilder[F](ec).resource.map(apply[F])
+}