Update advanced-saml-configurations.mdx

Added upstream params info

Author: clairekinde11

src/content/docs/authenticate/enterprise-connections/advanced-saml-configurations.mdx

@@ -56,3 +56,11 @@ Kinde-supported key attributes:
 - First Name / Last Name: Used for personalization or internal system mapping.
 
 Only configure key attributes if supported by your IdP.
+
+## Upstream parameters
+
+You can pass provider-specific parameters to an Identity Provider (IdP) during authentication. These are also known as 'upstream params'. The values your pass can either be static per connection or dynamic per user.
+
+You can use upstream paramsto create a smoother sign in experience - by passing the email through, or to offer an account switcher (such as the Google account switcher) during sign in.
+
+Note that every identity provider has their own set of supported parameters and values, so you'll need to check their documentation to determine which URL parameters are supported.