Move generation of gpx_file XML from model to builder

app/views/api/traces/_trace.builder

@@ -0,0 +1,22 @@
+# basic attributes
+
+attrs = {
+  "id" => trace.id,
+  "name" => trace.name,
+  "user" => trace.user.display_name,
+  "visibility" => trace.visibility,
+  "pending" => trace.inserted ? "false" : "true",
+  "timestamp" => trace.timestamp.xmlschema
+}
+
+if trace.inserted
+  attrs["lat"] = trace.latitude.to_s
+  attrs["lon"] = trace.longitude.to_s
+end
+
+xml.gpx_file(attrs) do |trace_xml_node|
+  trace_xml_node.description(trace.description)
+  trace.tags.each do |t|
+    trace_xml_node.tag(t.tag)
+  end
+end

app/views/api/traces/trace.builder

@@ -0,0 +1,9 @@
+xml.instruct! :xml, :version => "1.0"
+
+# basic attributes
+
+xml.osm(OSM::API.new.xml_root_attributes) do |osm|
+  @traces.each do |trace|
+    osm << render(:partial => "api/traces/trace.builder", :locals => { :trace => trace })
+  end
+end