Currently, when using the doc_count aggregation in Elastic Stack to create Service Level Objectives (SLOs), there is no need to provide a field because the doc_count aggregation simply counts documents regardless of any specific field.

However, when trying to configure an SLO in Terraform using the terraform-provider-elasticstack, the configuration requires that the field be filled out, which causes a validation error when using the doc_count aggregation, as this field is not needed for this type of aggregation.

Expected Behavior:
I would like the terraform-provider-elasticstack provider to allow the use of the doc_count aggregation without requiring the field parameter. When the doc_count aggregation is selected, the field should be optional since Elastic Stack does not require this parameter for counting documents.

Proposed Solution:
Update the provider to allow the doc_count aggregation to be used without requiring the field parameter. When doc_count is selected as the aggregation type, the field should be optional and not trigger validation errors. This change would align Terraform's behavior with how doc_count works in Kibana Console and the Elastic Stack API.