Allow more options on Secp256k1KeyPair.generate()

[sondreb]

The Secp256k1KeyPair.from() method allows specifying the .id and .controller using the options argument, while the generate only allows secureRandom and sets both id and controller automatically.

I know this library is for "did:key", but it would be nice to use similar pattern on both generate and from, and not having to override the id and controller for alternative DID Methods. Thanks!

[OR13]

https://github.com/transmute-industries/verifiable-data/tree/main/packages/secp256k1-key-pair

^ we're planning on making all the did key libraries in this repo small wrappers around these "LDKeyPair" classes in our mono repo...

We tend to think of did:key are just a format for keys, and we often start with it and then assign new values for id and controller when using did:web or sidetree did methods.

On proposed solution to this might be to make the options for LDKeyPair.generate look like this:

{
  secureRandom:  () => UInt8Array,
  id?: string,
  type?: string,
  controller?: string,
}