Implement group relationship endpoints

[Jodenee]

Is your feature request related to a problem? Please describe.
Relationship endpoints for groups are not implemented.

If your feature is related to implementing a new Roblox API, provide information here.

Group Relationship Docs

• Relationship endpoints
  • GET /v1/groups/{groupId}/relationships/{groupRelationshipType} - get relationships
  • DELETE /v1/groups/{groupId}/relationships/{groupRelationshipType}/{relatedGroupId} - remove a relationship
  • POST /v1/groups/{groupId}/relationships/{groupRelationshipType}/{relatedGroupId} - request a relationship with another group
• Relationship request endpoints
  • GET /v1/groups/{groupId}/relationships/{groupRelationshipType}/requests - get relationship requests
  • DELETE /v1/groups/{groupId}/relationships/{groupRelationshipType}/requests - batch remove relationship requests
  • POST /v1/groups/{groupId}/relationships/{groupRelationshipType}/requests - batch accept relationship requests
  • DELETE /v1/groups/{groupId}/relationships/{groupRelationshipType}/{relatedGroupId} - remove relationship request
  • POST /v1/groups/{groupId}/relationships/{groupRelationshipType}/requests/{relatedGroupId} - accept relationship request

Documented: Yes

Describe the solution you'd like

Add new enum GroupRelationType.

The following classes should be added

• GroupRelationship
• GroupRelationshipRequest

The following methods should be added

• BaseGroup.get_relationships()
• GroupRelationship.remove()
• BaseGroup.request_relationship()
• BaseGroup.get_relationship_requests()
• BaseGroup.decline_relationship_requests()
• BaseGroup.accept_relationship_requests()
• GroupRelationshipRequest.decline()
• GroupRelationshipRequest.accept()

[Jodenee]

I'll add this