Adding methods to remove writeOnlyProperties from model

[johnttompkins]

Issue #, if available:

Description of changes: Adding some methods to the ResourceSchema class to determine if a given model has writeOnlyProperties and also a method to remove the properties. Tried to make it extensible so that the same thing could be applied to other groups of properties.

I did not handle cases for writeOnlyProperties that were items in arrays, as I was unsure on if this was allowed or what the behavior should be. Say, if "/properties/arrayProperty/0" is writeOnly, and the array has two items, if we remove one, then the object still appears to have a writeOnlyProperty after removal:

{
   "arrayProperty": [0, 1]
}

After:

{
   "arrayProperty": [1] //still has item at "/properties/arrayProperty/0"
}

Input on this would be great.

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.

[rjlohan]

Agree we don't need to support array items here. Either the whole array property is writeOnly or not.

[rjlohan]

My overall thinking is;

• the handler should redact its own writeOnlyProperties (or they are redacted by the downstream service) for READ
• our contract tests should assert that writeOnlyProperties are not returned by READ
• CloudFormation's "dynamic references feature for SecretsManager and SSM SecureString is a service capability that describes how CloudFormation will handle those secrets inside the engine. This capability does not overlap with the handler platform

Hence, if someone uses those template semantics for resource properties which are not writeOnlyProperties, then the promise does not flow down to the READ handler.