requestbody: Add Caddyfile support (#3859)

* Add Caddyfile support for request_body:

```
  request_body {
    max_size 10000000
  }
```

* Improve Caddyfile parser for request_body module

* Remove unnecessary `continue`

* Add sample for caddyfile_adapt_test

1 files changed, 45 insertions, 0 deletions

diff --git a/caddytest/integration/caddyfile_adapt/request_body.txt b/caddytest/integration/caddyfile_adapt/request_body.txt
new file mode 100644
index 0000000..458b739
--- /dev/null
+++ b/caddytest/integration/caddyfile_adapt/request_body.txt
@@ -0,0 +1,45 @@
+localhost
+request_body {
+  max_size 1MB
+}
+----------
+{
+	"apps": {
+		"http": {
+			"servers": {
+				"srv0": {
+					"listen": [
+						":443"
+					],
+					"routes": [
+						{
+							"match": [
+								{
+									"host": [
+										"localhost"
+									]
+								}
+							],
+							"handle": [
+								{
+									"handler": "subroute",
+									"routes": [
+										{
+											"handle": [
+												{
+													"handler": "request_body",
+													"max_size": 1000000
+												}
+											]
+										}
+									]
+								}
+							],
+							"terminal": true
+						}
+					]
+				}
+			}
+		}
+	}
+}
\ No newline at end of file