Conditional DeploymentPreference not supported

[hgl]

Description:

I want to disable DeploymentPreference for staging and only enable for prod, it seems it's not supported.

Steps to reproduce the issue:

Conditions:
  IsProd: !Equals [ !Ref Stage, prod ]
Function:
  Type: AWS::Serverless::Function
  Properties:
    DeploymentPreference:
      Enabled: !If [ IsProd, true, false ]
      Type: Canary10Percent10Minutes

Observed result:

Failed with

Resource with id [Function] is invalid. 'Enabled' must be a boolean value

Expected result:

It should deploy.

[ShreyaGangishetty]

@hgl This is staged for release in v1.20.0. Please track the fix here #1196