feat: support record.key entries

[aldoborrero]

What

• Addition of the possibility of adding an extra key argument to records variable to disambiguate specific scenarios where collisions may occur.
• Addition of extra - to records key generation to better align with rest of the codebase.

Why

• Currently, we can't specify records that may produce the same id but with different values like the example below (which are valid ones):

module "test" {
  source  = "cloudposse/zone/cloudflare"
  version = "0.1.2"

  context            = module.test_label.context
  zone                = "example.com"
  zone_enabled = false
  enabled           = true
  records            = [
   {
      name    = "@"
      priority  = 1
      ttl          = 1
      type      = "MX"
      value    = "a.example.com"
    },
    {
      name     = "@"
      priority   = 5
      ttl           = 1
      type       = "MX"
      value     = "b.example.com"
    },
  ]
}

This PR changes this with the addition of a key resource:

module "test" {
  source  = "cloudposse/zone/cloudflare"
  version = "0.1.2"

  context            = module.test_label.context
  zone                = "example.com"
  zone_enabled = false
  enabled           = true
  records            = [
   {
      key        = "@-MX-1"
      name     = "@"
      priority   = 1
      ttl           = 1
      type       = "MX"
      value     = "a.example.com"
    },
    {
      key        = "@-MX-2"
      name     = "@"
      priority   = 5
      ttl           = 1
      type       = "MX"
      value     = "b.example.com"
    },
  ]
}

The key can be applied optionally to the records that needs them. It doesn't force to define one in all records.

References

• Closes Improve records interface to allow for multiple records with unique values #15

[milldr]

/test all

[milldr]

Looks good! Thank you for your contribution