We are getting ready in migrating an on premise SharePoint 2013 site to SharePoint Online. The on premise site though leverages CMIS that helps the users leverage this web service to automate the addition or removal of users to existing SharePoint security groups and also to help set up or manage unique permissions against folders in document libraries. Since CMIS is not compatible what could be a good replacement that would allow our user base in relying in web service calls that can allow in manage user management to SharePoint security groups and managing unique permissions against folders in document libraries. Thank you!
I think we need more details of what you want to achieve here...in the SPO World, calling SPO Web Services is not an option so you have to use SPO APIs (REST / CSOM) and Office 365 Graph API...you can call this APIs directly or through a services layer you provision in Azure or even OnPremises