feat(utilities): implement signing and verification for the "run on apify" links

[B4nan]

Allows hashing of an Actor input together with some metadata into a shareable link for the "Run on Apify" button. Uses a common secret for checking the signatures.

The hash consists of 3 parts separated by a dot, as in ABC.DEF.GHI, each being a base64url encoded string:

• meta object with the version and user properties.
• data object (the one that gets encoded)
• signature used for verification of the URL hash, computed from the meta and data objects

const manager = new CodeHashManager(secret);
const hash = manager.encode(input, '123'); // '123' is a user id

console.log(hash);

const { data, meta } = manager.decode(hash);

expect(input).toEqual(data);
expect(meta).toEqual({
    version: 1,
    user: '123',
    validSignature: true,
});

Closes #400

[valekjo]

Nice, thanks.