Frameworks / packages / cryptography calls updates; minor fix in SignedLicense constructor

[fraluderin]

This PR includes:

1. NuGet packages update (testing project);
2. Replaced obsolete constructors 'new MD5CryptoServiceProvider()' and 'new SHA512CryptoServiceProvider()' with 'MD5.Create()' and 'SHA512.Create()' as per Microsoft documentation;
3. Frameworks update (.net5 and net framework 4.6.1 are no longer supported);
4. Updated SignedLicense construtor to properly pass parameter 'issueDate' instead of DateTime.Now;
5. Removed unnecessary using statements.

Note - I didn't update package release notes / version as I don't know how to properly handle this, let me know if I have to make this change before merging.

[fraluderin]

Closed as I found an issue in tests - reopening when issue is solved.

[fraluderin]

Reopened PR, tests updated and OK on net core and net framework. At the moment my development environment settings does not allow me to test on netstandard 2.0.

[fraluderin]

@JanDotNet sorry for this question... is anyone still maintaining this wonderful project?

[JanDotNet]

@JanDotNet sorry for this question... is anyone still maintaining this wonderful project?

Hey fraluderin,

thank you for your contribution, for updating the code / framework dependencies and for the cleanup! This project is still maintained. I have few small comments to your PR. If that is fixed, I'll do some additional tests (there a other improvements that has not been published yet) and publish a new nuget version.

[fraluderin]

Hi @JanDotNet, thank you. Yes, I fixed that. What can I do to improve my contribution?