Override blocking inside CatsMonadError

Fix #1991

effects/cats/src/main/scala/sttp/client3/impl/cats/CatsMonadError.scala

@@ -21,4 +21,6 @@ class CatsMonadError[F[_]](implicit F: Sync[F]) extends MonadError[F] {
   override def flatten[T](ffa: F[F[T]]): F[T] = F.flatten(ffa)
 
   override def ensure[T](f: F[T], e: => F[Unit]): F[T] = F.guaranteeCase(f)(_ => e)
+
+  override def blocking[T](t: => T): F[T] = F.blocking(t)
 }

effects/cats/src/test/scala/sttp/client3/impl/cats/CatsMonadErrorTest.scala

@@ -0,0 +1,32 @@
+package sttp.client3.impl.cats
+
+import cats.effect.IO
+import cats.effect.unsafe.{IORuntime, IORuntimeConfig}
+import org.scalatest.freespec.AsyncFreeSpec
+
+class CatsMonadErrorTest extends AsyncFreeSpec {
+  import scala.concurrent.duration._
+
+  "blocking" - {
+    "should shift to blocking execution context " in {
+      implicit val ioRuntime: IORuntime = createIORuntime(computePoolSize = 1)
+      val monad = new CatsMonadError[IO]
+
+      val program = monad
+        .blocking(Thread.sleep(100.millis.toMillis))
+        .background
+        .use(getOutcome => IO.race(getOutcome, IO.unit))
+
+      program
+        .flatMap(either => IO.delay(assert(either.isRight)))
+        .unsafeToFuture()
+    }
+  }
+
+  private def createIORuntime(computePoolSize: Int): IORuntime = {
+    val (compute, _) = IORuntime.createWorkStealingComputeThreadPool(computePoolSize)
+    val (blocking, _) = IORuntime.createDefaultBlockingExecutionContext()
+
+    IORuntime(compute, blocking, compute, () => (), IORuntimeConfig())
+  }
+}