Add support for groups :

[aanchan]

• [x] Create three groups on the dev user pool correspoding to the three different logical user groupings
• [x] If possible remove from Cognito the custom attribute that depends on the accountAccessType
• [x] Remove the dependence on the deployment type on the front-end : https://github.com/SynaptitudeBrainHealth/synap_platform_frontend/blob/a1118ecc66796af45caaf2ea991fa419d0c98ce9/src/app/pages/registration/registration.service.ts#L107
• [x] Add a post-confirmation event to our verification AWS Lambda function to add a user to a default group :https://lifesaver.codes/answer/how-to-add-user-to-group