Added VersionDescription property on Serverless::Function

[Buffer0x7cd]

Issue #, if available:
#823
Description of changes:
This PR Add an Additional VersionDescription property on Serverless::Function.
Description of how you validated changes:
I validated the changes by creating an instance of SamFunction and then setting the VersionDescription property of the instance. after this i called the to_cloudformation method of SamFunction and validated that the string passed in VersionDescription is proprly set on the instance of LambdaVersion class under Description property.

Checklist:

• [ x] Write/update tests
• [ x] make pr passes
• Update documentation: For the Documentation I was not sure which part to update. I though i need to add this inside the Version/2016-10-31 . but i thought asked this explicitly will be better.

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

[codecov-io]

Codecov Report

Merging #835 into develop will increase coverage by 0.33%.
The diff coverage is 100%.

@@             Coverage Diff             @@
##           develop     #835      +/-   ##
===========================================
+ Coverage    94.23%   94.56%   +0.33%     
===========================================
  Files           67       67              
  Lines         2688     2834     +146     
  Branches       478      508      +30     
===========================================
+ Hits          2533     2680     +147     
- Misses          80       82       +2     
+ Partials        75       72       -3

Impacted Files	Coverage Δ
samtranslator/model/sam_resources.py	95.5% <100%> (-0.25%)	⬇️
samtranslator/plugins/api/implicit_api_plugin.py	96.35% <0%> (-3.65%)	⬇️
samtranslator/model/intrinsics.py	94.44% <0%> (-1.02%)	⬇️
samtranslator/sdk/resource.py	100% <0%> (ø)	⬆️
samtranslator/model/eventsources/cloudwatchlogs.py	100% <0%> (ø)	⬆️
samtranslator/model/api/api_generator.py	96.17% <0%> (+0.04%)	⬆️
samtranslator/model/eventsources/pull.py	92% <0%> (+0.33%)	⬆️
samtranslator/swagger/swagger.py	98.32% <0%> (+0.39%)	⬆️
samtranslator/model/__init__.py	98.11% <0%> (+1.25%)	⬆️
... and 1 more

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[keetonian]

Hey! This looks great so far. Could you add this property into one of the E2E tests? The one at the path tests/translator/input/function_with_alias.yaml should be a good candidate. Once that one is updated, you'll have to add the field into the output files at tests/translator/output/function_with_alias.yaml, tests/translator/output/aws-us-gov/function_with_alias.yaml, and tests/translator/output/aws-cn/function_with_alias.yaml.

After that, this should be good to go! Thank you for contributing!

[Buffer0x7cd]

Hey! @keetonian , Thanks for the response. I have updated the end to end tests as per your suggestion. please let me know if there are any other updates needed.

[keetonian]

This looks good! Thank you for the contribution! Just add the new property to the documentation and we'll be able to merge it in.

[keetonian]

@Buffer0x7cd Documentation- you have the file correct. You should add the property and a short description about it to https://github.com/awslabs/serverless-application-model/blob/develop/versions/2016-10-31.md#awsserverlessfunction

[jlhood]

Great work! Just make the documentation update @keetonian mentioned and this will be good to go!

[Buffer0x7cd]

@jlhood I have added the VersionDescription Property in the documentation as requested. please feel free to review this PR.

Issue has been fixed.