API work for group creation and retrieving all groups

[Assadbintahir]

In this issue, we will do the work for group creation and retrieving all groups

Expected Request and Response payloads can be found in the following design document:

https://docs.google.com/document/d/1_nU1UZaU3T9iIp-Xhf_k8RMaefjnom8LzOE_5_42xTQ/edit#

[Assadbintahir]

I have completed work on this. Create Group:

Retrieve list of groups:

Code for this is in Mapping repository. Assigning @dayemsiddiqui to test this.

[dayemsiddiqui]

I have tested this. This issue can be closed now.

FYI @jekram

[jekram]

Thanks @Assadbintahir @dayemsiddiqui