I want to setup Users/groups/roles/tenants in flowable but without using IDM UI, should be via spring boot/java API’s as requirement is to run the flowable workflow using REST API’s rather than just using flowable UI to do so.
All of those can be created through the service API of the IDM engine: https://github.com/flowable/flowable-engine/blob/master/modules/flowable-idm-api/src/main/java/org/flowable/idm/api/IdmIdentityService.java
are there any predefined tables for storing user/group etc in flowable IDM to leverage or we need to configure our own tables for the same?
Indeed, there are basic out of the box tables behind those service API’s.
to present a more complete solution, there is almost complete DB schema in this link which i suggest you take a look at.