feat(registry): add default for name in create namespace request (#1780)

Co-authored-by: Rémy Léone <[email protected]>

Author: scaleway-bot

cmd/scw/testdata/test-all-usage-registry-namespace-create-usage.golden

@@ -6,7 +6,7 @@ USAGE:
   scw registry namespace create [arg=value ...]
 
 ARGS:
-  name                Define a namespace name
+  name=<generated>    Define a namespace name
   [description]       Define a description
   [project-id]        Project ID to use. If none is passed the default project ID will be used
   [is-public]         Define the default visibility policy

internal/namespaces/registry/v1/registry_cli.go

@@ -233,6 +233,7 @@ func registryNamespaceCreate() *core.Command {
 				Required:   true,
 				Deprecated: false,
 				Positional: false,
+				Default:    core.RandomValueGenerator("ns"),
 			},
 			{
 				Name:       "description",