Add endpoint for cloud subnets

[lfu]

#1013

@miq-bot add_label enhancement, kasparov/no

[miq-bot]

Checked commit lfu@0e8c648 with ruby 2.6.3, rubocop 0.82.0, haml-lint 0.35.0, and yamllint
2 files checked, 3 offenses detected

app/controllers/api/cloud_subnets_controller.rb

• ❗ - Line 19, Col 32 - Naming/MethodParameterName - Method parameter must be at least 3 characters long.
• ❗ - Line 30, Col 29 - Naming/MethodParameterName - Method parameter must be at least 3 characters long.
• ❗ - Line 40, Col 31 - Naming/MethodParameterName - Method parameter must be at least 3 characters long.

[lfu]

POST /api/cloud_subnets
{
         "action" : "create",
         "resource" : {
           "ems_id" : 10000000000013,
           "name"   : "test_cloud_subnet"
         }
}

{
    "results": [
        {
            "success": true,
            "message": "Creating Cloud Subnet test_cloud_subnet for Provider: OpenStack Network Manager",
            "task_id": "10000000053334",
            "task_href": "http://localhost:3000/api/tasks/10000000053334"
        }
    ]
}

POST /api/cloud_subnets/10000000000028
{
         "action": "edit",
         "status": "available"
}

{
    "success": true,
    "message": "Updating Cloud Subnet id: 10000000000028 name: 'provider'",
    "task_id": "10000000053335",
    "task_href": "http://localhost:3000/api/tasks/10000000053335"
}

[agrare]

ping @abellotti @bdunne

[abellotti]

shouldn't this be Cannot create cloud subnet ... same for the Update and Delete BadRequestError

[NickLaMuro]

Closing in favor of #1025 (which fixes the tests that are failing here)