support defining a custom name for ES domain endpoint

[MarwanBayadsi]

Describe the Feature

support defining a custom name for ES domain endpoint.

Expected Behavior

To provide the ability to define a custom endpoint for our ES domain. Expect to support this feature https://aws.amazon.com/about-aws/whats-new/2020/11/amazon-elasticsearch-service-now-supports-defining-a-custom-name-for-your-domain-endpoint/

Use Case

It makes it easier for users to access Kibana, and allows them to move to a new domain without updating their clients.

[vladarts]

Hi! Required changes has been release in the https://github.com/hashicorp/terraform-provider-aws/blob/v3.35.0/CHANGELOG.md aws provider version. Now it can be added to the module.