We are using Salesforce as IDP in SP initiated flow.

We need to configure users in Salesforce to be part of multiple groups(roles) and send those list of group(roles) values in SAML Assertion response as below :

        <saml2:Attribute Name="groupName" NameFormat="urn:oasis:names:tc:SAML:2.0:attrname-format:unspecified">
            <saml2:AttributeValue
                xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:type="xs:string">admin
            </saml2:AttributeValue>
            <saml2:AttributeValue
                xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:type="xs:string">support
            </saml2:AttributeValue>
        </saml2:Attribute>

How can i configure in salesforce for groupName attribute to send a array of values(multiple roles which user is part of) as shown above.
Also, how to add users to multiple groups.