resource/aws_dx_lag: Deprecate number_of_connections

[radeksimko]

This is to address the following test failures:

=== RUN   TestAccAwsDxConnectionAssociation_basic
--- FAIL: TestAccAwsDxConnectionAssociation_basic (17.22s)
    testing.go:513: Step 0 error: After applying this step and refreshing, the plan was not empty:
        
        DIFF:
        
        DESTROY/CREATE: aws_dx_connection_association.test
          connection_id: "dxcon-fft4eqt7" => "dxcon-fft4eqt7"
          lag_id:        "dxlag-fgktz5h3" => "<computed>" (forces new resource)
        DESTROY/CREATE: aws_dx_lag.test
          arn:                   "arn:aws:directconnect:us-west-2:*******:dxlag/dxlag-fgktz5h3" => "<computed>"
          connections_bandwidth: "1Gbps" => "1Gbps"
          force_destroy:         "true" => "true"
          location:              "EqSe2" => "EqSe2"
          name:                  "tf-dx-t90nd" => "tf-dx-t90nd"
          number_of_connections: "2" => "1" (forces new resource)

=== RUN   TestAccAwsDxConnectionAssociation_multiConns
--- FAIL: TestAccAwsDxConnectionAssociation_multiConns (17.12s)
    testing.go:513: Step 0 error: After applying this step and refreshing, the plan was not empty:
        
        DIFF:
        
        DESTROY/CREATE: aws_dx_connection_association.test1
          connection_id: "dxcon-ffzd1kty" => "dxcon-ffzd1kty"
          lag_id:        "dxlag-fh87u1zp" => "<computed>" (forces new resource)
        DESTROY/CREATE: aws_dx_connection_association.test2
          connection_id: "dxcon-fgeqoh9q" => "dxcon-fgeqoh9q"
          lag_id:        "dxlag-fh87u1zp" => "<computed>" (forces new resource)
        DESTROY/CREATE: aws_dx_lag.test
          arn:                   "arn:aws:directconnect:us-west-2:*******:dxlag/dxlag-fh87u1zp" => "<computed>"
          connections_bandwidth: "1Gbps" => "1Gbps"
          force_destroy:         "true" => "true"
          location:              "EqSe2" => "EqSe2"
          name:                  "tf-dx-3a2u0" => "tf-dx-3a2u0"
          number_of_connections: "3" => "1" (forces new resource)

The story is that AWS provisions connections & associations automatically per number_of_connections (as it's passed to the API). This makes further management of connections tricky because any new non-default connection created via aws_dx_connection_association will cause Amazon to bump number_of_connections and cause drift as the number of connections no longer matches the initial number.

Unfortunately there's no way to avoid automated provisioning as NumberOfConnections is a required field in the API and has to be > 0. For that reason I decided to apply similar approach we already apply in some other resources (e.g. route table) and that is to plan removal of these default connections & associations.

I didn't implement that as part of this PR though, because that would be a breaking change. The goal is to inform the user about how we're going to tackle it going forward and avoid the drift for now.

Test results

=== RUN   TestAccAwsDxConnectionAssociation_basic
--- PASS: TestAccAwsDxConnectionAssociation_basic (47.35s)
=== RUN   TestAccAwsDxConnectionAssociation_multiConns
--- PASS: TestAccAwsDxConnectionAssociation_multiConns (46.58s)
=== RUN   TestAccAwsDxConnection_basic
--- PASS: TestAccAwsDxConnection_basic (39.48s)
=== RUN   TestAccAwsDxConnection_tags
--- PASS: TestAccAwsDxConnection_tags (61.83s)
=== RUN   TestAccAwsDxLag_basic
--- PASS: TestAccAwsDxLag_basic (92.54s)
=== RUN   TestAccAwsDxLag_tags
--- PASS: TestAccAwsDxLag_tags (118.86s)
PASS
ok  	github.com/terraform-providers/terraform-provider-aws/aws	406.689s

[bflad]

LGTM

=== RUN   TestAccAwsDxConnection_basic
--- PASS: TestAccAwsDxConnection_basic (17.76s)
=== RUN   TestAccAwsDxConnectionAssociation_basic
--- PASS: TestAccAwsDxConnectionAssociation_basic (23.07s)
=== RUN   TestAccAwsDxLag_basic
--- PASS: TestAccAwsDxLag_basic (24.97s)
=== RUN   TestAccAwsDxConnection_tags
--- PASS: TestAccAwsDxConnection_tags (27.81s)
=== RUN   TestAccAwsDxConnectionAssociation_multiConns
--- PASS: TestAccAwsDxConnectionAssociation_multiConns (31.00s)
=== RUN   TestAccAwsDxLag_tags
--- PASS: TestAccAwsDxLag_tags (38.52s)

[bflad]

This has been released in version 1.10.0 of the AWS provider. Please see the Terraform documentation on provider versioning or reach out if you need any assistance upgrading.

[ghost]

I'm going to lock this issue because it has been closed for 30 days ⏳. This helps our maintainers find and focus on the active issues.

If you feel this issue should be reopened, we encourage creating a new issue linking back to this one for added context. Thanks!