Support login hint with Entra ID as SAML IdP

[ErikAndreas]

Federation with SAML to Entra ID does not seem to work with login hint setting ("Login hint in Authn request in Subject NameID") enabled

https://learn.microsoft.com/en-us/entra/identity-platform/single-sign-on-saml-protocol#subject

By either an Auth method setting ('IdP is Entra') or by some kind of discovery (looking at metadataurl or issuer?) the option to pass login hint by url could be offered (which would attach ?login_hint= to request url)