server/http: fix scatter table API and add document (pingcap#8424)

docs/tidb_http_api.md

@@ -90,6 +90,20 @@
     *Hint: For the index column which column type is timezone dependent, e.g. `timestamp`, convert its value to UTC
 timezone.*
 
+1. Scatter regions of the specified table, add a `scatter-range` scheduler for the PD and the range is same as the table range.
+
+    ```shell
+    curl -X POST http://{TiDBIP}:10080/tables/{db}/{table}/scatter
+    ```
+
+    **Note**: The `scatter-range` scheduler may conflict with the global scheduler, do not use it for long periods on the larger table.
+
+1. Stop scatter the regions, disable the `scatter-range` scheduler for the specified table.
+
+    ```shell
+    curl -X POST http://{TiDBIP}:10080/tables/{db}/{table}/stop-scatter
+    ```
+
 1. Get TiDB server settings
 
     ```shell

server/http_handler.go

@@ -774,8 +774,8 @@ func (h tableHandler) addScatterSchedule(startKey, endKey []byte, name string) e
 	}
 	input := map[string]string{
 		"name":       "scatter-range",
-		"start_key":  url.QueryEscape(string(startKey)),
-		"end_key":    url.QueryEscape(string(endKey)),
+		"start_key":  string(startKey),
+		"end_key":    string(endKey),
 		"range_name": name,
 	}
 	v, err := json.Marshal(input)