Add ning http headers class

services/git-bridge/src/main/java/uk/ac/ic/wlgitbridge/io/http/ning/NingHttpHeaders.java

@@ -0,0 +1,46 @@
+package uk.ac.ic.wlgitbridge.io.http.ning;
+
+import com.ning.http.client.FluentCaseInsensitiveStringsMap;
+import com.ning.http.client.HttpResponseHeaders;
+
+import java.util.*;
+
+public class NingHttpHeaders extends HttpResponseHeaders {
+
+    private final FluentCaseInsensitiveStringsMap map;
+
+    private NingHttpHeaders(FluentCaseInsensitiveStringsMap map) {
+        this.map = map;
+    }
+
+    public static NingHttpHeadersBuilder builder() {
+        return new NingHttpHeadersBuilder();
+    }
+
+    @Override
+    public FluentCaseInsensitiveStringsMap getHeaders() {
+        return map;
+    }
+
+    public static class NingHttpHeadersBuilder {
+
+        private final Map<String, Collection<String>> map;
+
+        private NingHttpHeadersBuilder() {
+            map = new HashMap<>();
+        }
+
+        public NingHttpHeadersBuilder addHeader(String key, String... values) {
+            map.computeIfAbsent(key, __ -> new ArrayList<>())
+                    .addAll(Arrays.asList(values));
+            return this;
+        }
+
+        public NingHttpHeaders build() {
+            return new NingHttpHeaders(
+                    new FluentCaseInsensitiveStringsMap(map));
+        }
+
+    }
+
+}