Support Azure Entra Id for saml single sign on.

## Hight Light known issue:
Signed SAML `AuthnRequest` is not fully supported yet by Azure Entra ID.
See also for more details:
[single-sign-on-saml-protocol#signature](https://learn.microsoft.com/en-us/azure/active-directory/develop/single-sign-on-saml-protocol#signature)