Hide sensitive parameters

[waipeng]

Overview

This pull request introduces hiding of Sensitive data output.

Puppet now has type Sensitive, which hides the content from logs, etc. Hide it similarly in output of octocatalog-diff, by using a trivial hash so that any diff will still be show.

See also: https://puppet.com/docs/puppet/5.3/lang_data_sensitive.html

Checklist

• Make sure that all of the tests pass, and fix any that don't. Just run rake in your checkout directory, or review the CI job triggered whenever you push to a pull request.
• Make sure that there is 100% test coverage by running rake coverage:spec or ignoring untestable sections of code with # :nocov comments. If you need help getting to 100% coverage please ask; however, don't just submit code with no tests.
• If you have added a new command line option, we would greatly appreciate a corresponding integration test that exercises it from start to finish. This is optional but recommended.
• If you have added any new gem dependencies, make sure those gems are licensed under the MIT or Apache 2.0 license. We cannot add any dependencies on gems licensed under GPL.
• If you have added any new gem dependencies, make sure you've checked in a copy of the .gem file into the vendor/cache directory.

[alexjfisher]

This works well with Sensitive[String] parameters, but not so much with Sensitive[Hash]...

TypeError: no implicit conversion of Hash into String
  /home/fishera/control-repo/vendor/bundle/ruby/2.5.0/bundler/gems/octocatalog-diff-957a8175d326/lib/octocatalog-diff/catalog-diff/differ.rb:470:in `digest'

[ahayworth]

@waipeng Thank you for this! We'll merge it into the 1.6.0 release. I did have to make a change on the release branch to get tests to pass - take a look here. I think that's a benign change, just a copying/pasting error most likely - but please do let me know if it seems wrong.

[waipeng]

Oh yes I forgot to update the test after this change. Thanks for maintaining this software, it is very useful to us!