Additional configuration properties that are available for string SCIM 2.0 attribute mappings include:

ldap-attribute-name
The name of the LDAP attribute (in the mapped representation of the source entry generated by the sync class) whose values will be used as the values of the SCIM 2.0 attribute. This is required.
single-valued
Indicates whether the SCIM 2.0 attribute is single-valued or multivalued. If this is true, then the SCIM 2.0 representation of the attribute value will be as a JSON string. If this is false, then the SCIM 2.0 representation of the attribute value will be as a JSON array of strings.

You can use the following example configuration change to create a string SCIM 2.0 attribute mapping:

dsconfig create-scim2-attribute-mapping \
     --mapping-name userName \
     --type string \
     --set scim-attribute-name:userName \
     --set ldap-attribute-name:uid \
     --set attribute-usage:fetch \
     --set attribute-usage:create-during-realtime-sync \
     --set attribute-usage:create-during-resync \
     --set attribute-usage:update-during-realtime-sync \
     --set attribute-usage:update-during-resync \
     --set single-valued:true