I have a community with community users created from contacts. I want to have a process which updates user record if a related contact record is updated. It works for Email, Phone and other fields, but doesn't work for Username. I receive an error message:
Error element myRule_1_A1 (FlowRecordUpdate). The flow tried to update these records: null. This error occurred: MIXED_DML_OPERATION: DML operation on setup object is not permitted after you have updated a non-setup object (or vice versa): User, original object: Contact. You can look up ExceptionCode values in the SOAP API Developer Guide.
I tried Process Builder, Workflow and trigger. Any suggestions on how this can be achieved?