server: Add GET /health endpoint

server/app/controllers/HealthController.scala

@@ -0,0 +1,14 @@
+package controllers
+
+import javax.inject.Inject
+
+import controllers.common.{MyJsonController, MyJsonControllerComponents}
+
+class HealthController @Inject() (
+    cc: MyJsonControllerComponents)
+    extends MyJsonController(cc) {
+
+  def check() = Action {
+    Ok
+  }
+}

server/conf/routes

@@ -3,6 +3,8 @@
 # https://www.playframework.com/documentation/latest/ScalaRouting
 # ~~~~
 
+GET   /health                controllers.HealthController.check()
+
 GET   /transactions/:txid    controllers.TransactionsController.getTransaction(txid: String)
 
 GET   /addresses/:address    controllers.AddressesController.getDetails(address: String)

server/test/controllers/HealthControllerSpec.scala

@@ -0,0 +1,18 @@
+package controllers
+
+import controllers.common.MyAPISpec
+import play.api.Application
+import play.api.test.Helpers._
+
+class HealthControllerSpec extends MyAPISpec {
+
+  val application: Application = guiceApplicationBuilder.build()
+
+  "GET /health" should {
+    "return OK" in {
+      val response = GET("/health")
+
+      status(response) mustEqual OK
+    }
+  }
+}