Updating App config should use primary (#32428)

For #28713

Refactored the PATH fleet/config end-point to use the primary DB node
for both persisting changes and fetching modified App Config to avoid
stale UI due to read replica delay.

changes/28713-gitops-checkbox-status-replica-env

@@ -0,0 +1 @@
+* Refactored PATH fleet/config end-point to use the primary DB node for both persisting changes and fetching modified App Config.

server/service/appconfig.go

@@ -825,7 +825,7 @@ func (svc *Service) ModifyAppConfig(ctx context.Context, p []byte, applyOpts fle
 	}
 
 	// retrieve new app config with obfuscated secrets
-	obfuscatedAppConfig, err := svc.ds.AppConfig(ctx)
+	obfuscatedAppConfig, err := svc.ds.AppConfig(ctxdb.RequirePrimary(ctx, true))
 	if err != nil {
 		return nil, err
 	}