[Users Management] Assign user to group in AWS Cognito

[MastalerzKamil]

Goal

Implementation plan

1. Create Construct for attaching user in authentication module
2. Create Lambda function for detaching user from group in AWS Cognito
3. Update schema by creating mutation that would create detach selected user from user group in AWS Cognito
4. Connect mutation with Lambda as Data Source by creating resolver for mutation
5. Adding Unit tests