Api group model completion

[secondaryfun]

• Related Issue (include '#'): https://github.com/CotripperPlatform/CoTrip/issues/649

• Description of changes made:

Location: one-to-many relationship to Group added on Location Model Profile: many-to-many relationship to Group added on Profile Model Posts: one-to-many relationship to Group added on Post Model

• Is the feature complete/bug resolved/etc..: yes

• Any known bugs/strange behavior: no

• Is there specific feedback you would like on these changes:

Please check logic for "on_delete":

• Post Model - on_delete=models.CASCADE

• Location Model - on_delete=models.PROTECT

• Profile - blank

• Screenshot(s): Profile:

[secondaryfun]

Resubmitted with different branch.