documentation: Refactor DNS

docs/configuration/dns/server/predefined.md

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+---
+icon: material/new-box
+---
+
+!!! question "Since sing-box 1.12.0"
+
+# Predefined
+
+### Structure
+
+```json
+{
+  "dns": {
+    "servers": [
+      {
+        "type": "predefined",
+        "tag": "",
+        "responses": []
+      }
+    ]
+  }
+}
+```
+
+### Fields
+
+#### responses
+
+==Required==
+
+List of [Response](#response-structure).
+
+### Response Structure
+
+```json
+{
+  "query": [],
+  "query_type": [],
+  "rcode": "",
+  "answer": [],
+  "ns": [],
+  "extra": []
+}
+```
+
+!!! note ""
+
+    You can ignore the JSON Array [] tag when the content is only one item
+
+### Response Fields
+
+#### query
+
+List of domain name to match.
+
+#### query_type
+
+List of query type to match.
+
+#### rcode
+
+The response code.
+
+| Value      | Value in the legacy rcode server | Description     |
+|------------|----------------------------------|-----------------|
+| `NOERROR`  | `success`                        | Ok              |
+| `FORMERR`  | `format_error`                   | Bad request     |
+| `SERVFAIL` | `server_failure`                 | Server failure  |
+| `NXDOMAIN` | `name_error`                     | Not found       |
+| `NOTIMP`   | `not_implemented`                | Not implemented |
+| `REFUSED`  | `refused`                        | Refused         |
+
+`NOERROR` will be used by default.
+
+#### answer
+
+List of text DNS record to respond as answers.
+
+Examples:
+
+| Record Type | Example                       |
+|-------------|-------------------------------|
+| `A`         | `localhost. IN A 127.0.0.1`   |
+| `AAAA`      | `localhost. IN AAAA ::1`      |
+| `TXT`       | `localhost. IN TXT \"Hello\"` |
+
+#### ns
+
+List of text DNS record to respond as name servers.
+
+#### extra
+
+List of text DNS record to respond as extra records.