feat: Adding variable collection support

[alfespa17]

This will allow to use variable collecion inside the provider

resource "terrakube_collection" "collection" {
  name            = "TERRAKUBE_SUPER_COLLECTION"
  organization_id = data.terrakube_organization.org.id
  description     = "Hello Worldd!"
  priority        = 10
}

resource "terrakube_collection_item" "sample1" {
  organization_id = data.terrakube_organization.org.id
  collection_id   = terrakube_collection.collection.id
  key             = "sample-env-var"
  value           = "sample-value2222"
  description     = "sample env varrrrr"
  category        = "ENV"
  sensitive       = false
  hcl             = false
}

resource "terrakube_collection_reference" "sample1" {
  organization_id = data.terrakube_organization.org.id
  collection_id   = terrakube_collection.collection.id
  workspace_id    = terrakube_workspace_cli.sample1.id
  description     = "sample descriptionnnnqerq"
}

This feature is supported from Terrakube version 2.24.0-beta.5

Fix #87