webdav: add Content-Type and fix status

Motivation:

For HTTP Third-party copy, the status code should be 202 (Accepted), but
dCache currently returns 200 (OK).

The Content-Type of the response is also not defined.

Modification:

Update response to include a Content-Type and to set the 202 status code
once the transfer has been started.

Result:

dCache COPY response is more in keeping with other storage systems.

Target: master
Requires-notes: no
Requires-book: no
Patch: https://rb.dcache.org/r/11490
Acked-by: Dmitry Litvintsev

modules/dcache-webdav/src/main/java/org/dcache/webdav/transfer/CopyFilter.java

@@ -406,7 +406,7 @@ private void processThirdPartyCopy(Request request, Response response)
                                    "Error performing OpenId Connect Token Exchange");
             }
         } else {
-            Optional<String> error =_remoteTransfers.acceptRequest(response.getOutputStream(),
+            Optional<String> error =_remoteTransfers.acceptRequest(response,
                     request.getHeaders(), getSubject(), getRestriction(), path,
                     remote, credential, direction, isVerificationRequired(),
                     overwriteAllowed);

modules/dcache-webdav/src/main/java/org/dcache/webdav/transfer/RemoteTransferHandler.java

@@ -21,6 +21,7 @@
 import com.google.common.util.concurrent.ListenableFuture;
 import eu.emi.security.authn.x509.X509Credential;
 import io.milton.http.Response;
+import io.milton.http.Response.Status;
 import org.eclipse.jetty.io.EndPoint;
 import org.eclipse.jetty.server.HttpConnection;
 import org.slf4j.Logger;
@@ -221,7 +222,7 @@ public long getPerformanceMarkerPeroid()
      * Start a transfer and block until that transfer is complete.
      * @return a description of the error, if there was a problem.
      */
-    public Optional<String> acceptRequest(OutputStream out, Map<String,String> requestHeaders,
+    public Optional<String> acceptRequest(Response response, Map<String,String> requestHeaders,
             Subject subject, Restriction restriction, FsPath path, URI remote,
             Object credential, Direction direction, boolean verification,
             boolean overwriteAllowed)
@@ -235,14 +236,16 @@ public Optional<String> acceptRequest(OutputStream out, Map<String,String> reque
                 ? EnumSet.of(TransferFlag.REQUIRE_VERIFICATION)
                 : EnumSet.noneOf(TransferFlag.class);
         ImmutableMap<String,String> transferHeaders = buildTransferHeaders(requestHeaders);
-        RemoteTransfer transfer = new RemoteTransfer(out, subject, restriction,
+        RemoteTransfer transfer = new RemoteTransfer(response.getOutputStream(), subject, restriction,
                 path, remote, credential, flags, transferHeaders, direction,
                 overwriteAllowed);
 
         long id;
 
         synchronized (_transfers) {
             id = transfer.start();
+            response.setStatus(Status.SC_ACCEPTED);
+            response.setContentTypeHeader("text/perf-marker-stream");
             _transfers.put(id, transfer);
         }
 
@@ -334,7 +337,6 @@ public RemoteTransfer(OutputStream out, Subject subject, Restriction restriction
                 FsPath path, URI destination, @Nullable Object credential,
                 EnumSet<TransferFlag> flags, ImmutableMap<String,String> transferHeaders,
                 Direction direction, boolean overwriteAllowed)
-                throws ErrorResponseException
         {
             _subject = subject;
             _restriction = restriction;