feature #6: implement PostgresJson

add Article, Citien and User Entities
implement Article.findById()

src/fr/dcproject/routes/Article.kt

@@ -0,0 +1,19 @@
+package fr.dcproject.routes
+
+import Paths
+import fr.postgresjson.serializer.serialize
+import io.ktor.application.call
+import io.ktor.locations.KtorExperimentalLocationsAPI
+import io.ktor.locations.get
+import io.ktor.response.respondText
+import io.ktor.routing.Route
+
+@KtorExperimentalLocationsAPI
+fun Route.article() {
+    get<Paths.ArticlesRequest> {
+        call.respondText("todo")
+    }
+    get<Paths.ArticleRequest> {
+        call.respondText(it.article.serialize())
+    }
+}