Allow option to skip tenant namespace creation

Add --skip-namespace flag to the 'create tenant' command to skip automatic
namespace creation when the namespace already exists.

Signed-off-by: Anshuman Singh <anshumanchauhan9@gmail.com>

cmd/flux/create_tenant_test.go

@@ -54,6 +54,11 @@ func TestCreateTenant(t *testing.T) {
 			args:   "create tenant dev-team --with-namespace=apps --cluster-role=custom-role --export",
 			assert: assertGoldenFile("./testdata/create_tenant/tenant-with-cluster-role.yaml"),
 		},
+		{
+			name:   "tenant with skip namespace",
+			args:   "create tenant dev-team --with-namespace=apps --cluster-role=cluster-admin --skip-namespace --export",
+			assert: assertGoldenFile("./testdata/create_tenant/tenant-with-skip-namespace.yaml"),
+		},
 	}
 
 	for _, tt := range tests {