Support importing accounts from google authenticator export url

[05storm26]

Support importing accounts from the URL exported by Google Authenticator export functionality.
The export generates a QR code that contains within an URL like this:

otpauth-migration://offline?data=urlencoded-base64-encoded-protobuff-binary-data

The protobuff protocol specifing the content is this:

syntax = "proto3";

// Copied from: https://github.com/beemdevelopment/Aegis/blob/master/app/src/main/proto/google_auth.proto

message MigrationPayload {
  enum Algorithm {
    ALGO_INVALID = 0;
    ALGO_SHA1 = 1;
  }

  enum OtpType {
    OTP_INVALID = 0;
    OTP_HOTP = 1;
    OTP_TOTP = 2;
  }

  message OtpParameters {
    bytes secret = 1;
    string name = 2;
    string issuer = 3;
    Algorithm algorithm = 4;
    int32 digits = 5;
    OtpType type = 6;
    int64 counter = 7;
  }

  repeated OtpParameters otp_parameters = 1;
  int32 version = 2;
  int32 batch_size = 3;
  int32 batch_index = 4;
  int32 batch_id = 5;
}

It would be great if there were an import-otpauth-migration subcommand which would take this kind of url as input and then import the accounts from it.