See https://tools.ietf.org/html/rfc4180, Common Format and MIME Type for Comma-Separated Values (CSV) Files.
The first line in the CSV file must contain the names as the column headers. Use the /cdprofilemgmt/v2.0/CSV/headerNames API to get the list of header names.
Only one CSV import request can be running for the specified tenant.
The maximum file size is 10MB.
Multiple group members are specified with a '|' delimiter which may be overridden with the optional multiValueDelimiter query parameter. The members may be specified by name or ID. For example, testuser or 50GSYHD4C3. Federated users cannot be members.
Attribute values that contain a special character (i.e. comma) must be enclosed in double quotes.
Entitlement required: manageUserGroups (Manage users and groups) or manageAllUserGroups (Synchronize users and groups) or manageUserStandardGroups (Manage users and standard groups), or manageGroups (Manage all groups but not their members), or manageStandardGroups (Manage standard groups but not their members), or manageGroupMembers (Manage all group and their members), or manageStandardGroupMembers (Manage standard groups and their members).
Note: You only need one entitlement, but you can have more than one.
post https://{tenanturl}/v2.0/CSV/importGroups