Implement initializeMint instruction

[nickcruz]

Description

Adds initializeMint instruction + some unit tests to ensure it's working as a low-level instruction. Note that I haven't tested it outside of serializing it in a transaction.

For some reference, I'm currently trying to support the equivalent of createNFT.ts in metaplex-android as I haven't seen it implemented.

This is part 1 of 2 new instructions I want to add to SolanaKT, the other being mintTo.

Implementation references

I translated initializeMint.ts, using the initializeAccount.ts TS and Android (this lib) implementations as references.

Then I ran some local TS code to get some serialized Transaction values.

Serialized Transaction Values

Expected serialized transaction values come from some reference TS code. I just used the latest code from https://github.com/metaplex-foundation/js/ to generate them.

import { initializeMintBuilder } from "@metaplex-foundation/js";
import { Keypair, PublicKey } from "@solana/web3.js";

const mintKeypair = Keypair.fromSecretKey(
  new Uint8Array([
    248, 245, 206, 215, 221, 248, 207, 125, 63, 204, 25, 40, 10, 180, 174,
    189, 124, 221, 111, 20, 34, 34, 147, 0, 194, 55, 115, 203, 41, 9, 128,
    188, 119, 48, 108, 85, 136, 220, 56, 7, 110, 148, 77, 217, 121, 23, 39,
    159, 71, 234, 16, 104, 242, 116, 18, 106, 192, 38, 254, 250, 104, 231,
    160, 240,
  ])
);
const mintAuthority = new PublicKey(
  "9Aq6XkUT8Nx2ztkpkUxc4HiVCFWKTJZWiLnhC94iofvy"
);
const freezeAuthority = new PublicKey(
  "22BMtVRGveoYeJyvYDHfJP5JMCRKTYbp3QMhxU1P8w1n"
);
console.log("mint public key:", mintKeypair.publicKey.toBase58());
console.log("mint secret key:", mintKeypair.secretKey.toString());
console.log("mint authority public key:", mintAuthority.toBase58());
console.log("freeze authority public key:", freezeAuthority.toBase58());
const tx = initializeMintBuilder({
  mint: mintKeypair,
  decimals: 9,
  mintAuthority,
  freezeAuthority,
}).toTransaction();

tx.recentBlockhash = "Eit7RCyhUixAe2hGBS8oqnw59QK3kgMMjfLME5bm9wRn";
tx.sign(mintKeypair);

console.log("base64 serialized tx:", tx.serialize().toString("base64"));

Code Style

This is my first contribution to SolanaKT and generally I tried to follow the existing style as much as I could, but took a bit of my own freedom in the unit test I added. Happy to adjust styles if needed!

[ajamaica]

Thanks a lot for adding this missing call to the token program. We appreciate your contributions.