multiple ExternalAuthnConfigurations in Shibboleth IdP5

[Cantor, Scott]

> For example, /Auth/Ext1 delegates authentication to one IdP and
> /Auth/Ext2 to another IdP.

If you want to proxy authentication to an IdP, that isn't what External is for, that's handled by the SAML login flow. External is for doing non-standard things and proxying via SAML is very standard. Or via OIDC using our RP plugin for that.

-- Scott