Add validate logic at ParseJwtToken

[sagilio]

Improve security by default, and keep the logic synced from other SDKs.

API proposal:

// old
public virtual CasdoorUser? ParseJwtToken(string token)
// new
public virtual CasdoorUser? ParseJwtToken(string token, bool validateToken = true)
// add (because it needs to sync the jwks from casdoor, this will be an async logic)
public virtual Task<CasdoorUser?> ParseJwtTokenAsync(string token, bool validateToken = true)

This will be a breaking change, need user change the param if someone does not want to validate the token.

[casbin-bot]

@seriouszyx @ComradeProgrammer @Resulte