Disable Data Value validations

[pivotaljohn]

First Class Feature Flags

As the person consuming a ytt library
When I don't want validations on Data Values to run (e.g. a number of those validations are inappropriate for my situation; failing validations are preventing me from getting downstream information [like looking at --debug output]; I'm in the middle of modifying the library and want validations to get out of my way; ...)
I want to be able to turn off validations en masse

That is: implement the Disable Validations use case for Data Values...

• on the command-line; and
• while .eval()'ing a private library

Clarifying:

• when --data-values-disable-validations=false (default), data values ARE validated for the root library and each evaluated library,
  • except for libraries evaluated with library.eval(data_values_disable_validations=True), in which case, data values are NOT validated for that library AND any libraries it evaluates.
• when --data-values-disable-validations=true, data values are NOT validated for any library, regardless.

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Experiments

As an early adopter
When Carvel releases pre-beta versions of features
I want to be able to opt into using those features, even though I know the APIs are unstable and/or there might be bugs.
So that I can try out those features and be able to give feedback about the UX.

For the first "experiment" allow users to enable ytt Validations.