allow disabling signature verification

[goldylucks]

Summary

This enables E2E testing w/o the need of manual signature verification, by doing:

$ DISABLE_SIGNATURE_VERIFICATION=true node path/to/app.js

Happy to add tests once you approve this direction

related issues:

• How to test? #1336
• authorize function doesn't get triggered #1339
• Adding unit tests examples to the documentation #383
• How To Add Testing #638

Requirements (place an x in each [ ])

• I've read and understood the Contributing Guidelines and have done my best effort to follow them.
• I've read and agree to the Code of Conduct.

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[filmaj]

I believe ExpressReceiver's signatureVerification boolean set to false achieves this same behaviour.

I will close this PR. If you think I am mistaken, let's please continue the discussion about this potential change in #1339.

[goldylucks]

oh wow, I've been trying to get that functionality for the past 2 weeks!

do add it to the documentation for testing