JacksonCborSerializer should use CBOR ofc, #28918

* When we updated to Jackson 2.10 (prior Akka 2.6.0) the new JsonFactoryBuilder
  was used. That doesn't preserve the formatParserFeatures and formatGeneratorFeatures
  from the base CBORFactory and therefore the format was plain JSON.

* rolling update compatibility

akka-serialization-jackson/src/test/scala/akka/serialization/jackson/JacksonSerializerSpec.scala

@@ -4,6 +4,7 @@
 
 package akka.serialization.jackson
 
+import java.nio.charset.StandardCharsets
 import java.time.Duration
 import java.time.Instant
 import java.time.LocalDateTime
@@ -17,6 +18,7 @@ import java.util.logging.FileHandler
 import scala.collection.immutable
 import scala.concurrent.duration.FiniteDuration
 import scala.concurrent.duration._
+
 import akka.actor.ActorRef
 import akka.actor.ActorSystem
 import akka.actor.Address
@@ -569,6 +571,17 @@ class JacksonJsonSerializerSpec extends JacksonSerializerSpec("jackson-json") {
       """)(sys => checkSerialization(Elephant("Dumbo", 1), sys))
       }
     }
+
+    // issue #28918
+    "cbor compatibility for reading json" in {
+      val msg = SimpleCommand("abc")
+      val jsonSerializer = serializerFor(msg)
+      jsonSerializer.identifier should ===(31)
+      val manifest = jsonSerializer.manifest(msg)
+      val bytes = jsonSerializer.toBinary(msg)
+      val deserialized = serialization().deserialize(bytes, 32, manifest).get
+      deserialized should be(msg)
+    }
   }
 }
 
@@ -626,6 +639,20 @@ abstract class JacksonSerializerSpec(serializerName: String)
     val manifest = serializer.manifest(obj)
     val serializerId = serializer.identifier
     val blob = serializeToBinary(obj)
+
+    // Issue #28918, check that CBOR format is used (not JSON).
+    if (blob.length > 0) {
+      serializer match {
+        case _: JacksonJsonSerializer =>
+          if (!JacksonSerializer.isGZipped(blob))
+            new String(blob.take(1), StandardCharsets.UTF_8) should ===("{")
+        case _: JacksonCborSerializer =>
+          new String(blob.take(1), StandardCharsets.UTF_8) should !==("{")
+        case _ =>
+          throw new IllegalArgumentException(s"Unexpected serializer $serializer")
+      }
+    }
+
     val deserialized = deserializeFromBinary(blob, serializerId, manifest, sys)
     deserialized should ===(obj)
   }