refactor: make pubkey optional for decoded_json in keystore in decode_str! function

[artemd24]

Motivation

There is not need to raise exception because of cheking pub keys further

Description

Change Map.fetch!(decoded_json, "pubkey") |> parse_binary!() to

pubkey =
      case Map.has_key?(decoded_json, "pubkey") do
        true -> Map.get(decoded_json, "pubkey") |> parse_binary!()
        false -> derived_pubkey
      end

+some tests added

Resolves #1084

Closes #1084

[MegaRedHand]

Hey there @artemd24! Thanks for your contribution!

As part of this issue, we need to handle when the "pubkey" field isn't specified. In that case, we need to ignore the following comparison against derived_pubkey, and set pubkey = derived_pubkey. Also, please add unit tests to this change (you can find examples in test/unit/keystore_test.exs).

[artemd24]

Hello @MegaRedHand!

I have actualized changes according to your comment.
If you have more improvement ideas, please write it, I'll make it up with pleasure!

[MegaRedHand]

Great work @artemd24 ! There seem to be some formatting errors. Please run mix format.

[artemd24]

@MegaRedHand thank you for helping me!
If you have more good first issues I will be glad to contribute

[MegaRedHand]

Thanks again for your contribution! 😄

[MegaRedHand]

@all-contributors please add @artemd24 for code

[allcontributors]

@MegaRedHand

I've put up a pull request to add @artemd24! 🎉