module synthetics: request_basicauth should be ignored if not supported

[simonrdz]

Describe the Feature

The request_basicauth is actually not supported for obvious reasons but it some cases it might be used and in this cases terraform should not show a diff to avoid to erase settings.

Add and ignore_changes lifecyle block should do the trick

Expected Behavior

When a basicauth is added via the Datadog synhtetics web console, terraform should not see diff.

Use Case

If I set a basicauth using a datadog secret using the web console I should not have a diff like the following

      - request_basicauth {
          - password                 = (sensitive value) -> null
          - type                     = "web" -> null
          - username                 = "{{ LOGIN_AUTH }}" -> null
        }

Describe Ideal Solution

  # Ignore not supported properties
  lifecycle {
    ignore_changes = [ request_basicauth ]
  }

Alternatives Considered

No response

Additional Context

terraform-datadog-platform/modules/synthetics/main.tf

Line 424 in 335aaf0

## request_basicauth is insecure and complex, so we do not support it at this time.