Add response_types_supported to OIDC configuration (#7533)
Add response_types_supported to OIDC configuration (#7533)

The OIDC Discovery standard requires the response_types_supported field
to be returned in the .well-known/openid-configuration response.

Also, the AWS IAM OIDC consumer won't accept Vault as an identity
provider without this field.

Based on examples in the OIDC Core documentation, it appears Vault
supports only the `id_token` flow, and thus that is the only value that
makes sense to be set in this field. See:

https://openid.net/specs/openid-connect-core-1_0.html#AuthorizationExamples
rnaveiras/vault,hashicorp/vault,hashicorp/vault,quixoten/vault,hashicorp/vault,rnaveiras/vault,rnaveiras/vault,hartsock/vault,rnaveiras/vault,quixoten/vault,joelthompson/vault,quixoten/vault,hartsock/vault,hashicorp/vault,kingland/vault,joelthompson/vault,hartsock/vault,hashicorp/vault,quixoten/vault,kingland/vault,hartsock/vault,joelthompson/vault,kingland/vault,joelthompson/vault,hartsock/vault,rnaveiras/vault,kingland/vault,hashicorp/vault,kingland/vault