Dns discovery custom resolver (#25937)

* Import service discovery from akka-management

* Rename extension to Discovery to go with akka-discovery name
* Rename interafce to ServiceDisovery
* Import config, aggregate and dns
* Discovery documentation
* Load isolated async-dns if not configured as default
* OSGi for discovery
* Remove warning for not using in production
* Fail if old akka management on classpath
* Only allow async dns to be loaded as an additional resolver
* Use method in all of service discovery, not mechanism
* Mima filter
* Add discovery to aggregate
* Set discovery mima versions
* DnsDiscoverySpec: Only run docker test if docker available

project/Dependencies.scala

@@ -148,6 +148,8 @@ object Dependencies {
 
   val actor = l ++= Seq(config, java8Compat.value)
 
+  val discovery = l ++= Seq(Test.junit, Test.scalatest.value)
+
   val testkit = l ++= Seq(Test.junit, Test.scalatest.value) ++ Test.metricsAll
 
   val actorTests = l ++= Seq(

project/MiMa.scala

@@ -24,7 +24,8 @@ object MiMa extends AutoPlugin {
     val versions: Seq[String] = {
       val akka24NoStreamVersions = Seq("2.4.0", "2.4.1")
       val akka25Versions = (0 to latestPatchOf25).map(patch ⇒ s"2.5.$patch")
-      val akka24StreamVersions = (2 to 12) map ("2.4." + _)
+      val akka24StreamVersions = (2 to 12).map("2.4." + _)
+      val akka25DiscoveryVersions = (19 to latestPatchOf25).map(patch => s"2.5.$patch")
       val akka24WithScala212 =
         (13 to latestPatchOf24)
           .map("2.4." + _)
@@ -35,17 +36,24 @@ object MiMa extends AutoPlugin {
         "akka-stream-testkit")
       val akka250NewArtifacts = Seq(
         "akka-persistence-query")
+      val akka2519NewArtifacts = Seq(
+        "akka-discovery"
+      )
 
       scalaBinaryVersion match {
         case "2.11" ⇒
-          if (akka250NewArtifacts.contains(projectName)) akka25Versions
+          if (akka2519NewArtifacts.contains(projectName))
+            akka25DiscoveryVersions
+          else if (akka250NewArtifacts.contains(projectName)) akka25Versions
           else {
             if (!akka242NewArtifacts.contains(projectName)) akka24NoStreamVersions
             else Seq.empty
           } ++ akka24StreamVersions ++ akka24WithScala212 ++ akka25Versions
 
         case "2.12" ⇒
-          if (akka250NewArtifacts.contains(projectName))
+          if (akka2519NewArtifacts.contains(projectName))
+            akka25DiscoveryVersions
+          else if (akka250NewArtifacts.contains(projectName))
             akka25Versions
           else
             akka24WithScala212 ++ akka25Versions

project/OSGi.scala

@@ -122,6 +122,8 @@ object OSGi {
 
   val testkit = exports(Seq("akka.testkit.*"))
 
+  val discovery = exports(Seq("akka.discovery.*"))
+
   val osgiOptionalImports = Seq(
     // needed because testkit is normally not used in the application bundle,
     // but it should still be included as transitive dependency and used by BundleDelegatingClassLoader