add private key validation test

[martgil]

This PR will add a private key validation test and update PgpKey class

close #1346 // if this PR closes an issue

issue #0000 // if it doesn't close the issue yet

Todo:

• validate private key in readMany() of pgp-keys.ts
• eliminate errors TypeError { message: 'prvPacket.validate is not a function' }
• complete the test for unencrypted private key, encrypted private key validation.

reference: FlowCrypt/flowcrypt-browser#4271

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Tests (delete all except exactly one):

• Tests will be added later (issue #...)
• Tests added or updated

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To be filled by reviewers

I have reviewed that this PR... (tick whichever items you personally focused on during this review):

• addresses the issue it closes (if any)
• code is readable and understandable
• is accompanied with tests, or tests are not needed
• is free of vulnerabilities
• is documented clearly and usefully, or doesn't need documentation

[martgil]

@IvanPizhenko sorry for any disturbance, sir. I would like to ask for any hints?

I'm trying to achieve the same way that sir, Roman did on FlowCrypt/flowcrypt-browser#4271 when validating the key.
I keep getting the error of prvPacket.validate is not a function even though I've added the .validate(): Promise<any>; on openpgp.d.ts type definition file. I feel like I'm still missing something but not sure exactly what it is.

I also tried to find any references for the .validate() but I only get results from the openpgp.d.ts and openpgp-keys.ts(browser extension) / pgpkey.ts(ios-repo)

Any feedback would be much appreciated 🙇🏻‍♂️ Thanks!

[IvanPizhenko]

@martgil .d.ts file is just type definitions for the Typescript compiler, it does not provide function implementation. I think browser extension may use modified version of openpgp.js with such custom function added. You better ask Roman about this.

[tomholub]

Likely, flowcrypt-ios uses an older version of OpenPGP.js than browser extension does.

@IvanPizhenko we could update the iOS OpenPGP.js to v5 (instead of FES, initially), what do you think? It won't be an easy task.

[IvanPizhenko]

@tomholub yes, we can try to do it.