Add validation for SecretsManagerKmsKeyId

[jonife]

Description of changes:
Added validation to SecretsManagerKmsKeyId

Description of how you validated changes:
validation will ensure that SecretsManagerKmsKeyId is of type string

Checklist:

• Add/update unit tests using:
  • Correct values
  • Bad/wrong values (None, empty, wrong type, length, etc.)
  • Intrinsic Functions
• Add/update integration tests
• make pr passes
• Update documentation
• Verify transformed template deploys and application functions as expected

Examples?

Please reach out in the comments, if you want to add an example. Examples will be
added to sam init through https://github.com/awslabs/aws-sam-cli-app-templates/

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

[codecov-commenter]

Codecov Report

Merging #2323 (a395a62) into develop (e7a1496) will increase coverage by 0.71%.
The diff coverage is 100.00%.

@@             Coverage Diff             @@
##           develop    #2323      +/-   ##
===========================================
+ Coverage    93.58%   94.29%   +0.71%     
===========================================
  Files           90       97       +7     
  Lines         6124     7116     +992     
  Branches      1260     1466     +206     
===========================================
+ Hits          5731     6710     +979     
- Misses         183      196      +13     
  Partials       210      210              

Impacted Files	Coverage Δ
samtranslator/__init__.py	100.00% <100.00%> (ø)
samtranslator/feature_toggle/dialup.py	100.00% <100.00%> (ø)
samtranslator/feature_toggle/feature_toggle.py	100.00% <100.00%> (+12.16%)	⬆️
samtranslator/intrinsics/actions.py	98.78% <100.00%> (+0.06%)	⬆️
samtranslator/intrinsics/resource_refs.py	95.83% <100.00%> (-0.17%)	⬇️
samtranslator/metrics/method_decorator.py	100.00% <100.00%> (ø)
samtranslator/metrics/metrics.py	100.00% <100.00%> (ø)
samtranslator/region_configuration.py	77.77% <0.00%> (-22.23%)	⬇️
samtranslator/validator/validator.py	91.80% <0.00%> (-3.85%)	⬇️
samtranslator/model/exceptions.py	97.67% <0.00%> (-2.33%)	⬇️
... and 43 more

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[jfuss]

Can we add unit tests as well? The end to end tests are great but we can create a better coverage if we add unit tests and validate different input (lists, dict, int, etc).

[jfuss]

Could we parameterize this to include anything that is not a string? We covered list here but would be good to add int, bool and dict to add move coverage.

[jfuss]

Thank you for going through additional iterations with adding more unit tests.