#1699, add relationshop to routing plan/group/rateplan and rate_group

[Ivanov-Anton]

Description

add has_many relationships between two API resources (routing_plan and routing_group)
add has_many relationships between two API resources (rateplan - rate_group)

Examples

how to add rate_group for a specific rate-plan

POST {{host}}/api/rest/admin/rateplans/{{last_created_rateplan_id}}/relationships/rate-groups

{
  "data": [
    { "type": "rate-groups", "id": "1" }
  ]
}

how to remove all rate-groups from rate-plan

PATCH {{host}}/api/rest/admin/rateplans/:id?include=rate-groups

{
    "data": {
        "type": "rateplans",
        "id": {{last_created_rateplan_id}},
        "relationships": {
            "rate-groups": {
                "data": []
            }
        }
    }
}

how to add a group to rate-plan (through PATCH request) when rate-plan already contains one group

PATCH {{host}}/api/rest/admin/rateplans/33?include=rate-groups

{
  "data": {
    "type": "rateplans",
    "id": "33",
    "relationships": {
      "rate-groups": {
        "data": [
          {"type": "rate-groups", "id": "1"}, // Existing group
          {"type": "rate-groups", "id": "2"}  // New group
        ]
      }
    }
  }
}

Additional links

closes #1699

[Ivanov-Anton]