First draft of implementation (#1)

* First draft of implementation

Readme will follow

* Rename id.

* Exclude `commons-io` to disable build warnings

* Simplify metrics and add documentation

src/test/java/io/kokuwa/keycloak/metrics/prometheus/PrometheusClient.java

@@ -0,0 +1,19 @@
+package io.kokuwa.keycloak.metrics.prometheus;
+
+import javax.ws.rs.Consumes;
+import javax.ws.rs.GET;
+import javax.ws.rs.Path;
+import javax.ws.rs.core.MediaType;
+
+/**
+ * JAX-RS client for prometheus endpoint.
+ *
+ * @author Stephan Schnabel
+ */
+public interface PrometheusClient {
+
+	@GET
+	@Path("/metrics")
+	@Consumes(MediaType.TEXT_PLAIN)
+	String scrap();
+}