Refactor lookup providers

- Create lookup strategy object to handle several provider
- New root ID server provider
- Refactor code into appropriate classes

src/main/groovy/io/kamax/mxisd/lookup/RootProvider.groovy

@@ -0,0 +1,34 @@
+package io.kamax.mxisd.lookup
+
+import groovy.json.JsonSlurper
+import io.kamax.mxisd.api.ThreePidType
+import org.springframework.stereotype.Component
+
+@Component
+class RootProvider implements ThreePidProvider {
+
+    private List<String> roots = Arrays.asList("https://matrix.org", "https://vector.im")
+    private JsonSlurper json = new JsonSlurper()
+
+    @Override
+    int getPriority() {
+        return 0
+    }
+
+    @Override
+    Optional<?> find(ThreePidType type, String threePid) {
+        for (String root : roots) {
+            HttpURLConnection rootSrvConn = (HttpURLConnection) new URL(
+                    "${root}/_matrix/identity/api/v1/lookup?medium=${type}&address=${threePid}"
+            ).openConnection()
+
+            def output = json.parseText(rootSrvConn.getInputStream().getText())
+            if (output['address'] != null) {
+                return Optional.of(output)
+            }
+        }
+
+        return Optional.empty()
+    }
+
+}