implemented LinkEnricher registration via Enrich annotation

scm-annotations/src/main/java/sonia/scm/api/v2/resources/Enrich.java

@@ -0,0 +1,26 @@
+package sonia.scm.api.v2.resources;
+
+import java.lang.annotation.Documented;
+import java.lang.annotation.ElementType;
+import java.lang.annotation.Retention;
+import java.lang.annotation.RetentionPolicy;
+import java.lang.annotation.Target;
+
+/**
+ * Annotation to specify the source of an enricher.
+ *
+ * @author Sebastian Sdorra
+ * @since 2.0.0
+ */
+@Documented
+@Target(ElementType.TYPE)
+@Retention(RetentionPolicy.RUNTIME)
+public @interface Enrich {
+
+  /**
+   * Source mapping class.
+   *
+   * @return source mapping class
+   */
+  Class<?> value();
+}