Go CLI: switch to admin/api server (#15861)

### What problem does this PR solve?

```
RAGFlow(api/default)> use admin
SUCCESS
RAGFlow(api/default)> use api 'abc';
SUCCESS
```

### Type of change

- [x] New Feature (non-breaking change which adds functionality)

---------

Signed-off-by: Jin Hai <haijin.chn@gmail.com>

internal/cli/common_command.go

@@ -713,10 +713,6 @@ func (c *CLI) AddAPIServer(cmd *Command) (ResponseIf, error) {
 		c.Config.APIClientConfig.APIServerMap[apiServerName].ApiToken = &apiServerToken
 	}
 
-	transport := &http.Transport{
-		TLSClientConfig: &tls.Config{InsecureSkipVerify: true},
-	}
-
 	if c.APIServerClientMap == nil {
 		c.APIServerClientMap = make(map[string]*HTTPClient)
 	}
@@ -725,6 +721,10 @@ func (c *CLI) AddAPIServer(cmd *Command) (ResponseIf, error) {
 		return nil, fmt.Errorf("api server: %s already exists", apiServerName)
 	}
 
+	transport := &http.Transport{
+		TLSClientConfig: &tls.Config{InsecureSkipVerify: true},
+	}
+
 	c.APIServerClientMap[apiServerName] = &HTTPClient{
 		Host:           apiServerIP,
 		Port:           apiServerPort,
@@ -788,6 +788,23 @@ func (c *CLI) AddAdminServer(cmd *Command) (ResponseIf, error) {
 		c.Config.AdminClientConfig.AdminPort = adminServerPort
 	}
 
+	transport := &http.Transport{
+		TLSClientConfig: &tls.Config{InsecureSkipVerify: true},
+	}
+
+	c.AdminServerClient = &HTTPClient{
+		Host:           adminServerIP,
+		Port:           adminServerPort,
+		APIVersion:     "v1",
+		ConnectTimeout: 5 * time.Second,
+		ReadTimeout:    60 * time.Second,
+		VerifySSL:      false,
+		client: &http.Client{
+			Transport: transport,
+			Timeout:   300 * time.Second,
+		},
+	}
+
 	var result SimpleResponse
 	result.Code = 0
 	result.Message = "admin server added successfully"
@@ -1027,3 +1044,62 @@ func FlattenMap(data map[string]interface{}, prefix string, result *[]map[string
 		}
 	}
 }
+
+func (c *CLI) UseAPIServer(cmd *Command) (ResponseIf, error) {
+	serverName, ok := cmd.Params["server_name"].(string)
+	if !ok {
+		return nil, fmt.Errorf("server_name not provided")
+	}
+
+	if c.Config.CLIMode == APIMode {
+		if c.Config.APIClientConfig.CurrentAPIServer == serverName {
+			return nil, fmt.Errorf("api server %s is already used", serverName)
+		}
+	}
+
+	var httpClient *HTTPClient
+	httpClient, ok = c.APIServerClientMap[serverName]
+	if !ok {
+		return nil, fmt.Errorf("api server %s not found", serverName)
+	}
+	if httpClient == nil {
+		return nil, fmt.Errorf("api server %s is nil", serverName)
+	}
+	var apiServerConfig *APIServerConfig
+	apiServerConfig, ok = c.Config.APIClientConfig.APIServerMap[serverName]
+	if !ok {
+		return nil, fmt.Errorf("api server %s not found in config", serverName)
+	}
+	if apiServerConfig == nil {
+		return nil, fmt.Errorf("api server %s is nil", serverName)
+	}
+
+	c.Config.APIClientConfig.CurrentAPIServer = serverName
+	c.Config.CLIMode = APIMode
+
+	var result SimpleResponse
+	result.Code = 0
+	result.Message = fmt.Sprintf("switch to api server %s", serverName)
+	result.Duration = 0
+	return &result, nil
+
+}
+
+func (c *CLI) UseAdminServer(cmd *Command) (ResponseIf, error) {
+
+	if c.Config.CLIMode == AdminMode {
+		return nil, fmt.Errorf("already in admin mode")
+	}
+
+	if c.AdminServerClient == nil || c.Config.AdminClientConfig == nil {
+		return nil, fmt.Errorf("admin server not added")
+	}
+
+	c.Config.CLIMode = AdminMode
+
+	var result SimpleResponse
+	result.Code = 0
+	result.Message = "switch to admin server"
+	result.Duration = 0
+	return &result, nil
+}