fix: limit anonymous request body (#5244)

* fix: limit anonymous request body (env ANONYMOUS_REQUEST_BODY_LIMIT_KB = 512)

* fix: allow disabling anonymous request body limit

constant/env.go

@@ -10,6 +10,7 @@ var GetMediaToken bool
 var GetMediaTokenNotStream bool
 var UpdateTask bool
 var MaxRequestBodyMB int
+var AnonymousRequestBodyLimitKB int
 var AzureDefaultAPIVersion string
 var NotifyLimitCount int
 var NotificationLimitDurationMinute int