Code review comment: The value of that is passed to the ctor of `VertxHttpExporter` by `OtlpRecorder` (same as for the gRPC exporter).  Furthermore, the tests already cover this

Code under review:
public void handle(HttpClientRequest request) {

                            HttpClientRequest clientRequest = request.response(new Handler<>() {
                                @Override
                                public void handle(AsyncResult<HttpClientResponse> callResult) {
                                    if (callResult.succeeded()) {
                                        HttpClientResponse clientResponse = callResult.result();
                                        clientResponse.body(new Handler<>() {
                                            @Override
                                            public void handle(AsyncResult<Buffer> bodyResult) {
                                                if (bodyResult.succeeded()) {
                                                    onResponse.accept(new Response() {
                                                        @Override
                                                        public int statusCode() {
                                                            return clientResponse.statusCode();
                                                        }

                                                        @Override
                                                        public String statusMessage() {
                                                            return clientResponse.statusMessage();
                                                        }

                                                        @Override
                                                        public byte[] responseBody() {
                                                            return bodyResult.result().getBytes();
                                                        }
                                                    });
                                                } else {
                                                    onError.accept(bodyResult.cause());
                                                }
                                            }
                                        });
                                    } else {
                                        onError.accept(callResult.cause());
                                    }
                                }
                            })
                                    .putHeader("Content-Type", contentType);

                            ByteArrayOutputStream os; 
                            if (compressionEnabled) {
                                os = new ByteArrayOutputStream(contentLength);
                                clientRequest.putHeader("Content-Encoding", "gzip");
                                try (var gzos = new GZIPOutputStream(os)) {
                                    marshaler.accept(gzos);
                                } catch (IOException e) {
                                    throw new IllegalStateException(e);
                                }
                            } else {
                                os = new NonCopyingByteArrayOutputStream(contentLength);
                                marshaler.accept(os);
                            }

                            if (!headers.isEmpty()) {
                                for (var entry : headers.entrySet()) {
                                    clientRequest.putHeader(entry.getKey(), entry.getValue());
                                }
                            }

                            clientRequest.send(Buffer.buffer(os.toByteArray()));

                        }

Line commented on: clientRequest.putHeader("Content-Encoding", "gzip");

Revised code:
public void handle(HttpClientRequest request) {

                            HttpClientRequest clientRequest = request.response(new Handler<>() {
                                @Override
                                public void handle(AsyncResult<HttpClientResponse> callResult) {
                                    if (callResult.succeeded()) {
                                        HttpClientResponse clientResponse = callResult.result();
                                        clientResponse.body(new Handler<>() {
                                            @Override
                                            public void handle(AsyncResult<Buffer> bodyResult) {
                                                if (bodyResult.succeeded()) {
                                                    onResponse.accept(new Response() {
                                                        @Override
                                                        public int statusCode() {
                                                            return clientResponse.statusCode();
                                                        }

                                                        @Override
                                                        public String statusMessage() {
                                                            return clientResponse.statusMessage();
                                                        }

                                                        @Override
                                                        public byte[] responseBody() {
                                                            return bodyResult.result().getBytes();
                                                        }
                                                    });
                                                } else {
                                                    onError.accept(bodyResult.cause());
                                                }
                                            }
                                        });
                                    } else {
                                        onError.accept(callResult.cause());
                                    }
                                }
                            })
                                    .putHeader("Content-Type", contentType);

                            ByteArrayOutputStream os; 
                            if (compressionEnabled) {
                                os = new ByteArrayOutputStream(contentLength);
                                clientRequest.putHeader("Content-Encoding", "gzip");
                                try (var gzos = new GZIPOutputStream(os)) {
                                    marshaler.accept(gzos);
                                } catch (IOException e) {
                                    throw new IllegalStateException(e);
                                }
                            } else {
                                os = new NonCopyingByteArrayOutputStream(contentLength);
                                marshaler.accept(os);
                            }

                            if (!headers.isEmpty()) {
                                for (var entry : headers.entrySet()) {
                                    clientRequest.putHeader(entry.getKey(), entry.getValue());
                                }
                            }

                            clientRequest.send(Buffer.buffer(os.toByteArray()));

                        }