You don’t state the nature of your SSO (Single Sign On?) in your email, but I guess it’s LDAP.
I’m not sure you can do this. You can use LDAP for GeoServer security, but I’ve not seen any indication it can be used for the database connections. I think the credentials must be hard-coded at store-creation time.
There was a security extension that uses JDBC to authenticate users (you are correct that this can be used allow GeoServer to benefit from any single sign on system you have already set up for your database).
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