// Create a "restricted" NS (no auth method specified).
ns := &namespace.NamespaceSpec{
  Name:  name,
  Regions: regions,
  MtlsAuth: &namespace.MtlsAuthSpec{}, /* or omitted */
  ApiKeyAuth: &namespace.ApiKeyAuthSpec{}, /* or omitted */
  RetentionDays: retention,
}

// Create a NS with mTLS auth.
ns := &namespace.NamespaceSpec{
  Name:  name,
  Regions: regions,
  MtlsAuth: &namespace.MtlsAuthSpec{
    AcceptedClientCa: clientCA,
    Enabled: true,
  },
  ApiKeyAuth: &namespace.ApiKeyAuthSpec{}, /* or omitted */
  RetentionDays: retention,
}

// Create a NS with API keys auth.
ns := &namespace.NamespaceSpec{
  Name:  name,
  Regions: regions,
  MtlsAuth: &namespace.MtlsAuthSpec{}, /* or omitted */
  ApiKeyAuth: &namespace.ApiKeyAuthSpec{
    Enabled: true,
  },
  RetentionDays: retention,
}

// Create a NS with mTLS and API key auth.
ns := &namespace.NamespaceSpec{
  Name:  name,
  Regions: regions,
  MtlsAuth: &namespace.MtlsAuthSpec{
    AcceptedClientCa: clientCA,
    Enabled: true,
  },
  ApiKeyAuth: &namespace.ApiKeyAuthSpec{
    Enabled: true,
  },
  RetentionDays: retention,
}