JCL-341: Omit Accept Turtle header when reading non-RDF resources (#445)

Author: acoburn

solid/src/main/java/com/inrupt/client/solid/SolidClient.java

@@ -123,7 +123,9 @@ public <T extends Resource> CompletionStage<T> read(final URI identifier, final
         decorateHeaders(builder, defaultHeaders);
         decorateHeaders(builder, headers);
 
-        builder.setHeader(ACCEPT, TEXT_TURTLE);
+        if (RDFSource.class.isAssignableFrom(clazz)) {
+            builder.setHeader(ACCEPT, TEXT_TURTLE);
+        }
 
         defaultHeaders.firstValue(USER_AGENT).ifPresent(agent -> builder.setHeader(USER_AGENT, agent));
         headers.firstValue(USER_AGENT).ifPresent(agent -> builder.setHeader(USER_AGENT, agent));

solid/src/test/java/com/inrupt/client/solid/SolidMockHttpService.java

@@ -159,6 +159,14 @@ private void setupMocks() {
                 .withStatus(204)));
 
         wireMockServer.stubFor(get(urlEqualTo("/binary"))
+            .atPriority(1)
+            .withHeader("User-Agent", equalTo(USER_AGENT))
+            .withHeader("Accept", containing("text/turtle"))
+            .willReturn(aResponse()
+                .withStatus(406)));
+
+        wireMockServer.stubFor(get(urlEqualTo("/binary"))
+            .atPriority(2)
             .withHeader("User-Agent", equalTo(USER_AGENT))
             .willReturn(aResponse()
                 .withStatus(200)