`cfn init` shows warning: Could not find specified format 'date-time' for type 'string'. Defaulting to 'String'

```shell
MacBook@ ~/workspace/test-r-p $ cfn --version
cfn 0.2.1
MacBook@ ~/workspace/test-r-p $ cfn init
Initializing new project
Do you want to develop a new resource(r) or a module(m)?.
>> r
What's the name of your resource type?
(Organization::Service::Resource)
>> mparnisa::test::rp
Select a language for code generation:
[1] go
[2] java
[3] python36
[4] python37
(enter an integer):
>> 2
Enter a package name (empty for default 'com.mparnisa.test.rp'):
>>
Choose codegen model - 1 (default) or 2 (guided-aws):
>> 1
Could not find specified format 'date-time' for type 'string'. Defaulting to 'String'
Could not find specified format 'date-time' for type 'string'. Defaulting to 'String'
Initialized a new project in /Users/mparnisa/workspace/test-r-p
```

In the RPDK log:

```
[2021-01-11T22:30:50Z] DEBUG - ResourceModel POJO: /Users/mparnisa/workspace-sync/test-r-p/target/generated-sources/rpdk/com/mparnisa/test/rp/ResourceModel.java
[2021-01-11T22:30:50Z] ERROR - Could not find specified format 'date-time' for type 'string'. Defaulting to 'String'
[2021-01-11T22:30:50Z] ERROR - Could not find specified format 'date-time' for type 'string'. Defaulting to 'String'
[2021-01-11T22:30:50Z] DEBUG - Overwriting '/Users/mparnisa/workspace-sync/test-r-p/target/generated-sources/rpdk/com/mparnisa/test/rp/ResourceModel.java'
```

Reproduce the warning with cfn 0.2.1 by running cfn init for a Java resource and selecting codegen model 1. Start with the generated ResourceModel.java path and the RPDK log entries shown in the report, then trace which generation step handles the date-time format. Done means cfn init completes without the reported warning and the generated model is produced as expected.

Written by the indexing model from the issue text.