I am going to venture a guess here as i am new to this as well. I have been using Spring version of SAML 2 authentication.
Looks like the SP wants to sign the authn request as shown in page 10 (bottom image) of your doc:
“SignAuthnRequest”: true,
To do this you will have to provide it with a signature key. In my case the SP setup requires to point to a keystore where this key exists and also the alias of the key to be used.
HI the SP name is only string and done successfully ,
but i need to used as a external authentication of oKTA , but in SAML they response me back with email id only , but i need more detail so i can used as authtentication
You can use the guide available here to set up the SAML application and also get the required IdP details that you can add in your service provider application.