AWS::OpsWorks::Stack - RdsDbInstances

## 1. Title
AWS::OpsWorks::Stack-RdsDbInstances

## 2. Scope of request
AWS::OpsWorks::Stack-RdsDbInstances when updated via CloudFormation causes all AWS::OpsWorks::Apps to lose database configuration.

## 3. Expected behavior

In Update, changing RdsDbInstances in the stack should result the in the apps also being updated to maintain the data source configuration.

It seems RdsDbInstances are deregistered and then created again, which causes the apps to lose their configuration since they are not being updated to include the new data source.

## 4. Suggest specific test cases

Just updating a password from a AWS::OpsWorks::Stack RdsDbInstances results in the described behavior.

## 5. Helpful Links to speed up research and evaluation

https://docs.aws.amazon.com/AWSCloudFormation/latest/UserGuide/aws-resource-opsworks-stack.html
https://docs.aws.amazon.com/AWSCloudFormation/latest/UserGuide/aws-resource-opsworks-app.html

## 6. Category

5. Management (CloudTrail, Config...)
11. Other (IoT, Migration, Budgets...)

Start with the AWS CloudFormation documentation for AWS::OpsWorks::Stack and AWS::OpsWorks::App, then reproduce the issue by changing an RdsDbInstances password. Done means updating the stack preserves each app's database configuration and the behavior is covered by a focused test case.

Written by the indexing model from the issue text.