Restructure, rename, modularize.

Change-Id: I4aa6cfb486fe002cf65405ec9c2876e3114aaf46
diff --git a/runtime/src/main/java/eu/mulk/quarkus/googlecloud/jsonlogging/Label.java b/runtime/src/main/java/eu/mulk/quarkus/googlecloud/jsonlogging/Label.java
new file mode 100644
index 0000000..02f7034
--- /dev/null
+++ b/runtime/src/main/java/eu/mulk/quarkus/googlecloud/jsonlogging/Label.java
@@ -0,0 +1,8 @@
+package eu.mulk.quarkus.googlecloud.jsonlogging;
+
+public record Label(String key, String value) {
+
+  public static Label of(String key, String value) {
+    return new Label(key, value);
+  }
+}