Moving a group as a subgroup of another group does not send group invitation

[oseg]

Scenario:

• Create group A as an open group
• Many users join group A
• Create group B without members (except owner)
• Move group A as a subgroup of group B

Results:
=> group A members are still members of group A, but they are not members of its parent group: group B and invitations to group B are not sent.

Expected results:
=> group A members should have left group A, should have receive a notification of the group move and should have receive a new invitation to join group A