Use content_length method for setting the Content-Length header

Boost.Beast changed the signature of the previously used generic `set`
method so that it no longer accepts integer types, however there is
alreay a more specific method for setting the Content-Length header, so
use this one instead.

lib/perfdata/elasticsearchwriter.cpp

@@ -494,7 +494,7 @@ void ElasticsearchWriter::SendRequest(const String& body)
 		request.set(http::field::authorization, "Basic " + Base64::Encode(username + ":" + password));
 
 	request.body() = body;
-	request.set(http::field::content_length, request.body().size());
+	request.content_length(request.body().size());
 
 	/* Don't log the request body to debug log, this is already done above. */
 	Log(LogDebug, "ElasticsearchWriter")

lib/perfdata/influxdbwriter.cpp

@@ -517,7 +517,7 @@ void InfluxdbWriter::Flush()
 	}
 
 	request.body() = body;
-	request.set(http::field::content_length, request.body().size());
+	request.content_length(request.body().size());
 
 	try {
 		if (stream.first) {

lib/remote/configfileshandler.cpp

@@ -84,7 +84,7 @@ bool ConfigFilesHandler::HandleRequest(
 		response.result(http::status::ok);
 		response.set(http::field::content_type, "application/octet-stream");
 		response.body() = content;
-		response.set(http::field::content_length, response.body().size());
+		response.content_length(response.body().size());
 	} catch (const std::exception& ex) {
 		HttpUtility::SendJsonError(response, params, 500, "Could not read file.",
 			DiagnosticInformation(ex));

lib/remote/httpserverconnection.cpp

@@ -186,7 +186,7 @@ bool EnsureValidHeaders(
 		} else {
 			response.set(http::field::content_type, "text/html");
 			response.body() = String("<h1>Bad Request</h1><p><pre>") + errorMsg + "</pre></p>";
-			response.set(http::field::content_length, response.body().size());
+			response.content_length(response.body().size());
 		}
 
 		response.set(http::field::connection, "close");
@@ -259,7 +259,7 @@ bool HandleAccessControl(
 					response.set(http::field::access_control_allow_methods, "GET, POST, PUT, DELETE");
 					response.set(http::field::access_control_allow_headers, "Authorization, Content-Type, X-HTTP-Method-Override");
 					response.body() = "Preflight OK";
-					response.set(http::field::content_length, response.body().size());
+					response.content_length(response.body().size());
 					response.set(http::field::connection, "close");
 
 					boost::system::error_code ec;
@@ -290,7 +290,7 @@ bool EnsureAcceptHeader(
 		response.result(http::status::bad_request);
 		response.set(http::field::content_type, "text/html");
 		response.body() = "<h1>Accept header is missing or not set to 'application/json'.</h1>";
-		response.set(http::field::content_length, response.body().size());
+		response.content_length(response.body().size());
 		response.set(http::field::connection, "close");
 
 		boost::system::error_code ec;
@@ -331,7 +331,7 @@ bool EnsureAuthenticatedUser(
 		} else {
 			response.set(http::field::content_type, "text/html");
 			response.body() = "<h1>Unauthorized. Please check your user credentials.</h1>";
-			response.set(http::field::content_length, response.body().size());
+			response.content_length(response.body().size());
 		}
 
 		boost::system::error_code ec;
@@ -423,7 +423,7 @@ bool EnsureValidBody(
 		} else {
 			response.set(http::field::content_type, "text/html");
 			response.body() = String("<h1>Bad Request</h1><p><pre>") + ec.message() + "</pre></p>";
-			response.set(http::field::content_length, response.body().size());
+			response.content_length(response.body().size());
 		}
 
 		response.set(http::field::connection, "close");

lib/remote/httputility.cpp

@@ -58,7 +58,7 @@ void HttpUtility::SendJsonBody(boost::beast::http::response<boost::beast::http::
 
 	response.set(http::field::content_type, "application/json");
 	response.body() = JsonEncode(val, params && GetLastParameter(params, "pretty"));
-	response.set(http::field::content_length, response.body().size());
+	response.content_length(response.body().size());
 }
 
 void HttpUtility::SendJsonError(boost::beast::http::response<boost::beast::http::string_body>& response,

lib/remote/infohandler.cpp

@@ -92,7 +92,7 @@ bool InfoHandler::HandleRequest(
 
 		body += R"(<p>More information about API requests is available in the <a href="https://icinga.com/docs/icinga2/latest/" target="_blank">documentation</a>.</p></html>)";
 		response.body() = body;
-		response.set(http::field::content_length, response.body().size());
+		response.content_length(response.body().size());
 	}
 
 	return true;