Add ByteBuf parameter HttpConversionUtil (#10785)

Motivation:
`HttpConversionUtil#toFullHttpResponse` and `HttpConversionUtil#toFullHttpRequest` has `ByteBufAllocator` which is used for building `FullHttpMessage` and then data can be appended with `FullHttpMessage#content`. However, there can be cases when we already have `ByteBuf` ready with data. So we need a parameter to add `ByteBuf` directly into `FullHttpMessage` while creating it.

Modification:
Added `ByteBuf` parameter,

Result:
More functionality for handling `FullHttpMessage` content.

codec-http2/src/main/java/io/netty/handler/codec/http2/HttpConversionUtil.java

@@ -14,6 +14,7 @@
  */
 package io.netty.handler.codec.http2;
 
+import io.netty.buffer.ByteBuf;
 import io.netty.buffer.ByteBufAllocator;
 import io.netty.handler.codec.UnsupportedValueConverter;
 import io.netty.handler.codec.http.DefaultFullHttpRequest;
@@ -212,12 +213,30 @@ public final class HttpConversionUtil {
      * @throws Http2Exception see {@link #addHttp2ToHttpHeaders(int, Http2Headers, FullHttpMessage, boolean)}
      */
     public static FullHttpResponse toFullHttpResponse(int streamId, Http2Headers http2Headers, ByteBufAllocator alloc,
+                                                      boolean validateHttpHeaders) throws Http2Exception {
+        return toFullHttpResponse(streamId, http2Headers, alloc.buffer(), validateHttpHeaders);
+    }
+
+    /**
+     * Create a new object to contain the response data
+     *
+     * @param streamId The stream associated with the response
+     * @param http2Headers The initial set of HTTP/2 headers to create the response with
+     * @param content {@link ByteBuf} content to put in {@link FullHttpResponse}
+     * @param validateHttpHeaders <ul>
+     *        <li>{@code true} to validate HTTP headers in the http-codec</li>
+     *        <li>{@code false} not to validate HTTP headers in the http-codec</li>
+     *        </ul>
+     * @return A new response object which represents headers/data
+     * @throws Http2Exception see {@link #addHttp2ToHttpHeaders(int, Http2Headers, FullHttpMessage, boolean)}
+     */
+    public static FullHttpResponse toFullHttpResponse(int streamId, Http2Headers http2Headers, ByteBuf content,
                                                       boolean validateHttpHeaders)
                     throws Http2Exception {
         HttpResponseStatus status = parseStatus(http2Headers.status());
         // HTTP/2 does not define a way to carry the version or reason phrase that is included in an
         // HTTP/1.1 status line.
-        FullHttpResponse msg = new DefaultFullHttpResponse(HttpVersion.HTTP_1_1, status, alloc.buffer(),
+        FullHttpResponse msg = new DefaultFullHttpResponse(HttpVersion.HTTP_1_1, status, content,
                                                            validateHttpHeaders);
         try {
             addHttp2ToHttpHeaders(streamId, http2Headers, msg, false);
@@ -245,15 +264,32 @@ public final class HttpConversionUtil {
      * @throws Http2Exception see {@link #addHttp2ToHttpHeaders(int, Http2Headers, FullHttpMessage, boolean)}
      */
     public static FullHttpRequest toFullHttpRequest(int streamId, Http2Headers http2Headers, ByteBufAllocator alloc,
-                                                boolean validateHttpHeaders)
+                                                    boolean validateHttpHeaders) throws Http2Exception {
-                    throws Http2Exception {
+        return toFullHttpRequest(streamId, http2Headers, alloc.buffer(), validateHttpHeaders);
+    }
+
+    /**
+     * Create a new object to contain the request data
+     *
+     * @param streamId The stream associated with the request
+     * @param http2Headers The initial set of HTTP/2 headers to create the request with
+     * @param content {@link ByteBuf} content to put in {@link FullHttpRequest}
+     * @param validateHttpHeaders <ul>
+     *        <li>{@code true} to validate HTTP headers in the http-codec</li>
+     *        <li>{@code false} not to validate HTTP headers in the http-codec</li>
+     *        </ul>
+     * @return A new request object which represents headers/data
+     * @throws Http2Exception see {@link #addHttp2ToHttpHeaders(int, Http2Headers, FullHttpMessage, boolean)}
+     */
+    public static FullHttpRequest toFullHttpRequest(int streamId, Http2Headers http2Headers, ByteBuf content,
+                                                boolean validateHttpHeaders) throws Http2Exception {
         // HTTP/2 does not define a way to carry the version identifier that is included in the HTTP/1.1 request line.
         final CharSequence method = checkNotNull(http2Headers.method(),
                 "method header cannot be null in conversion to HTTP/1.x");
         final CharSequence path = checkNotNull(http2Headers.path(),
                 "path header cannot be null in conversion to HTTP/1.x");
         FullHttpRequest msg = new DefaultFullHttpRequest(HttpVersion.HTTP_1_1, HttpMethod.valueOf(method
-                        .toString()), path.toString(), alloc.buffer(), validateHttpHeaders);
+                        .toString()), path.toString(), content, validateHttpHeaders);
         try {
             addHttp2ToHttpHeaders(streamId, http2Headers, msg, false);
         } catch (Http2Exception e) {