caddyfile: Implement heredoc support (#5385)

caddytest/integration/caddyfile_adapt/heredoc.txt

@@ -0,0 +1,50 @@
+example.com {
+    respond <<EOF
+    <html>
+      <head><title>Foo</title>
+      <body>Foo</body>
+    </html>
+    EOF 200
+}
+----------
+{
+	"apps": {
+		"http": {
+			"servers": {
+				"srv0": {
+					"listen": [
+						":443"
+					],
+					"routes": [
+						{
+							"match": [
+								{
+									"host": [
+										"example.com"
+									]
+								}
+							],
+							"handle": [
+								{
+									"handler": "subroute",
+									"routes": [
+										{
+											"handle": [
+												{
+													"body": "\u003chtml\u003e\n  \u003chead\u003e\u003ctitle\u003eFoo\u003c/title\u003e\n  \u003cbody\u003eFoo\u003c/body\u003e\n\u003c/html\u003e\n",
+													"handler": "static_response",
+													"status_code": 200
+												}
+											]
+										}
+									]
+								}
+							],
+							"terminal": true
+						}
+					]
+				}
+			}
+		}
+	}
+}

caddytest/integration/caddyfile_adapt/import_args_snippet.txt

@@ -1,6 +1,6 @@
 (logging) {
 	log {
-		output file /var/log/caddy/{args.0}.access.log
+		output file /var/log/caddy/{args[0]}.access.log
 	}
 }
 

caddytest/integration/caddyfile_adapt/reverse_proxy_options.txt

@@ -6,7 +6,7 @@ https://example.com {
 		method GET
 		rewrite /rewritten?uri={uri}
 
-		buffer_requests
+		request_buffers 4KB
 
 		transport http {
 			read_buffer 10MB
@@ -54,7 +54,6 @@ https://example.com {
 										{
 											"handle": [
 												{
-													"buffer_requests": true,
 													"handler": "reverse_proxy",
 													"headers": {
 														"request": {
@@ -68,6 +67,7 @@ https://example.com {
 															}
 														}
 													},
+													"request_buffers": 4000,
 													"rewrite": {
 														"method": "GET",
 														"uri": "/rewritten?uri={http.request.uri}"

caddytest/integration/testdata/import_respond.txt

@@ -1 +1 @@
-respond "'I am {args.0}', hears {args.1}"
+respond "'I am {args[0]}', hears {args[1]}"