I am trying to send User, Contact and Account related fields through SAML Response. But while configuring the SAML attributes in the Connected App, I only see User, Profile, Org, and few more Objects but not Contact and Account. Salesforce doc says JIT searches User record based on Contact.Email and Contact.Lastname. I am not finding Contact object.
Custom attributes in a Connected app to be used in SAML configuration can only be on the User object. This is from the documentation:
A custom attribute can be any custom field added to the User object in the organization, as long as it is one of the following data types: Email, Text, URL, or Formula (with Text Return Type). After you select Custom Attribute for the Subject Type, Salesforce displays a Custom Attribute field with a list of the available User object custom fields in the organization.
The statement that you are referring highlights how JIT works in case of Community when it finds the Subject in the assertion, and compares it with Contact fields.