Fixes the `TestAccAWSDBEventSubscription_basicUpdate` acceptance test
`TestAccAWSDBEventSubscription_importBasic` is still failing, but has been failing since November.
* provider/aws: Allow `source_ids` in `aws_db_event_subscription` to be
Updatable
Fixes#7809
This commit adds support for `source_ids` to be updated rather than
forcing new each time. Unfortunately, it must range over the difference
in the source_ids and add and remove them 1 at a time. AWS does not
support batch updating source_ids
```
% make testacc TEST=./builtin/providers/aws TESTARGS='-run=TestAccAWSDBEventSubscription_'
==> Checking that code complies with gofmt requirements...
go generate $(go list ./... | grep -v /terraform/vendor/)
TF_ACC=1 go test ./builtin/providers/aws -v
-run=TestAccAWSDBEventSubscription_ -timeout 120m
=== RUN TestAccAWSDBEventSubscription_basicUpdate
--- PASS: TestAccAWSDBEventSubscription_basicUpdate (1277.87s)
=== RUN TestAccAWSDBEventSubscription_withSourceIds
--- PASS: TestAccAWSDBEventSubscription_withSourceIds (1012.96s)
PASS
ok github.com/hashicorp/terraform/builtin/providers/aws
2290.844s
```
* Update resource_aws_db_event_subscription.go
Jake Champlin