Updates an existing custom provider. When issuer or discoveryUrl changes on an OIDC provider, the server re-fetches and validates the discovery document before persisting.
The provider identifier, for example `custom:mycompany`.
The fields to update on the provider.
final CustomOAuthProvider provider =
await supabase.auth.admin.customProviders.updateProvider(
'custom:mycompany',
UpdateCustomProviderParams(
customClaimsAllowlist: ['groups', 'org_id', 'mail'],
),
);