Optionally require a valid content type for all rest requests with content (#22691)

This change adds a strict mode for xcontent parsing on the rest layer. The strict mode will be off by default for 5.x and in a separate commit will be enabled by default for 6.0. The strict mode, which can be enabled by setting `http.content_type.required: true` in 5.x, will require that all incoming rest requests have a valid and supported content type header before the request is dispatched. In the non-strict mode, the Content-Type header will be inspected and if it is not present or not valid, we will continue with auto detection of content like we have done previously.

The content type header is parsed to the matching XContentType value with the only exception being for plain text requests. This value is then passed on with the content bytes so that we can reduce the number of places where we need to auto-detect the content type.

As part of this, many transport requests and builders were updated to provide methods that
accepted the XContentType along with the bytes and the methods that would rely on auto-detection have been deprecated.

In the non-strict mode, deprecation warnings are issued whenever a request with body doesn't provide the Content-Type header.

See #19388 

1 files changed, 11 insertions, 0 deletions

diff --git a/core/src/main/java/org/elasticsearch/client/support/AbstractClient.java b/core/src/main/java/org/elasticsearch/client/support/AbstractClient.java
index b93c00ca9f..5a789af3ee 100644
--- a/core/src/main/java/org/elasticsearch/client/support/AbstractClient.java
+++ b/core/src/main/java/org/elasticsearch/client/support/AbstractClient.java
@@ -343,6 +343,7 @@ import org.elasticsearch.common.bytes.BytesReference;
 import org.elasticsearch.common.component.AbstractComponent;
 import org.elasticsearch.common.settings.Settings;
 import org.elasticsearch.common.util.concurrent.ThreadContext;
+import org.elasticsearch.common.xcontent.XContentType;
 import org.elasticsearch.tasks.TaskId;
 import org.elasticsearch.threadpool.ThreadPool;
 
@@ -1082,6 +1083,11 @@ public abstract class AbstractClient extends AbstractComponent implements Client
         }
 
         @Override
+        public PutPipelineRequestBuilder preparePutPipeline(String id, BytesReference source, XContentType xContentType) {
+            return new PutPipelineRequestBuilder(this, PutPipelineAction.INSTANCE, id, source, xContentType);
+        }
+
+        @Override
         public void deletePipeline(DeletePipelineRequest request, ActionListener<WritePipelineResponse> listener) {
             execute(DeletePipelineAction.INSTANCE, request, listener);
         }
@@ -1132,6 +1138,11 @@ public abstract class AbstractClient extends AbstractComponent implements Client
         }
 
         @Override
+        public SimulatePipelineRequestBuilder prepareSimulatePipeline(BytesReference source, XContentType xContentType) {
+            return new SimulatePipelineRequestBuilder(this, SimulatePipelineAction.INSTANCE, source, xContentType);
+        }
+
+        @Override
         public void allocationExplain(ClusterAllocationExplainRequest request, ActionListener<ClusterAllocationExplainResponse> listener) {
             execute(ClusterAllocationExplainAction.INSTANCE, request, listener);
         }