add hazard metadata class

src/hazard/src/main/java/gov/usgs/earthquake/nshmp/netcdf/www/HazardMetadata.java

+package gov.usgs.earthquake.nshmp.netcdf.www;
+
+import gov.usgs.earthquake.nshmp.gmm.Imt;
+import gov.usgs.earthquake.nshmp.gmm.NehrpSiteClass;
+import gov.usgs.earthquake.nshmp.netcdf.Nshm;
+import gov.usgs.earthquake.nshmp.netcdf.www.Metadata.ServiceResponseMetadata;
+import gov.usgs.earthquake.nshmp.netcdf.www.Request.RequestData;
+import gov.usgs.earthquake.nshmp.netcdf.www.RequestHazardCurves.HazardRequestDataImt;
+
+/**
+ * Hazard metadata.
+ *
+ * @author U.S. Geological Survey
+ */
+public class HazardMetadata {
+
+  static class HazardResponseMetadata extends ServiceResponseMetadata {
+    public final Nshm nshm;
+    public final Imt imt;
+
+    HazardResponseMetadata(
+        Nshm nshm,
+        NehrpSiteClass siteClass,
+        Imt imt,
+        String xLabel,
+        String yLabel) {
+      super(siteClass, xLabel, yLabel);
+      this.nshm = nshm;
+      this.imt = imt;
+    }
+
+    @Override
+    public HazardRequestDataImt toRequestMetadata(RequestData requestData) {
+      return new HazardRequestDataImt(nshm, requestData.site, siteClass, imt, requestData.format);
+    }
+  }
+}