Toggle Validation on Debug Flag

[adamrushy]

Issue being fixed or feature implemented

The issue is that validation will fail when running locally because it's trying to run the chain of trust during development which isn't required.

What was done?

Added a debug condition to avoid running this validation. I guess a more better approach would be to be able run a list of validations so that the client could exclude the signature validation in debug but generally, I think this is fine?

Checklist:

• [ ] I have performed a self-review of my own code
• [ ] I have commented my code, particularly in hard-to-understand areas
• [ ] I have added or updated relevant unit/integration/functional/e2e tests
• [ ] I have made corresponding changes to the documentation

[adamrushy]

Fixes: https://github.com/tikhop/TPInAppReceipt/issues/126

@tikhop would you be happy with this approach for now?