MM-59283: Minor improvement in getClientConfig (#27825)

Overall, there is no bug here. But opportunities for
improvement.
- Used the maps.Clone function.
- Handled the error while writing to the network.

https://mattermost.atlassian.net/browse/MM-59283
```release-note
NONE
```

server/channels/api4/config.go

@@ -258,7 +258,9 @@ func getClientConfig(c *Context, w http.ResponseWriter, r *http.Request) {
 		config = c.App.Srv().Platform().ClientConfigWithComputed()
 	}
 
-	w.Write([]byte(model.MapToJSON(config)))
+	if err := json.NewEncoder(w).Encode(config); err != nil {
+		c.Logger.Warn("Error while writing response", mlog.Err(err))
+	}
 }
 
 func getEnvironmentConfig(c *Context, w http.ResponseWriter, r *http.Request) {

server/channels/app/platform/config.go

@@ -13,6 +13,7 @@ import (
 	"encoding/json"
 	"errors"
 	"fmt"
+	"maps"
 	"net/http"
 	"reflect"
 	"strconv"
@@ -307,10 +308,7 @@ func (ps *PlatformService) EnsureAsymmetricSigningKey() error {
 
 // LimitedClientConfigWithComputed gets the configuration in a format suitable for sending to the client.
 func (ps *PlatformService) LimitedClientConfigWithComputed() map[string]string {
-	respCfg := map[string]string{}
+	respCfg := maps.Clone(ps.LimitedClientConfig())
-	for k, v := range ps.LimitedClientConfig() {
-		respCfg[k] = v
-	}
 
 	// These properties are not configurable, but nevertheless represent configuration expected
 	// by the client.
@@ -321,10 +319,7 @@ func (ps *PlatformService) LimitedClientConfigWithComputed() map[string]string {
 
 // ClientConfigWithComputed gets the configuration in a format suitable for sending to the client.
 func (ps *PlatformService) ClientConfigWithComputed() map[string]string {
-	respCfg := map[string]string{}
+	respCfg := maps.Clone(ps.ClientConfig())
-	for k, v := range ps.clientConfig.Load().(map[string]string) {
-		respCfg[k] = v
-	}
 
 	// These properties are not configurable, but nevertheless represent configuration expected
 	// by the client.
@@ -340,7 +335,6 @@ func (ps *PlatformService) ClientConfigWithComputed() map[string]string {
 	} else {
 		respCfg["SchemaVersion"] = strconv.Itoa(ver)
 	}
-
 	return respCfg
 }