feat: add support for configurable registries and applicable authentication options

[micsco]

This adds support per #66

Resolves #66

[merceyz]

Could you do this without using npm-registry-fetch?
This PR increases the bundle size by 1MB and startup time by about 82% and that seems a bit excessive for essentially adding a few headers.

$ hyperfine "node ./dist-before/corepack.js --version" "node ./dist-after/corepack.js --version"
Benchmark 1: node ./dist-before/corepack.js --version
  Time (mean ± σ):      49.7 ms ±   0.6 ms    [User: 47.4 ms, System: 3.6 ms]
  Range (min … max):    48.9 ms …  52.0 ms    57 runs

Benchmark 2: node ./dist-after/corepack.js --version
  Time (mean ± σ):      90.7 ms ±   1.5 ms    [User: 83.9 ms, System: 8.3 ms]
  Range (min … max):    89.2 ms …  95.1 ms    33 runs

Summary
  'node ./dist-before/corepack.js --version' ran
    1.82 ± 0.04 times faster than 'node ./dist-after/corepack.js --version'

[micsco]

@merceyz - Per your suggestion, I removed the dependencies and manually added the appropriate headers.

Now I see the following results when benchmarking:

$ hyperfine "node ./dist-before/corepack.js --version" "node ./dist-after/corepack.js --version"
Benchmark 1: node ./dist-before/corepack.js --version
  Time (mean ± σ):      55.9 ms ±   2.1 ms    [User: 49.8 ms, System: 7.8 ms]
  Range (min … max):    53.9 ms …  65.2 ms    47 runs

Benchmark 2: node ./dist-after/corepack.js --version
  Time (mean ± σ):      56.2 ms ±   2.1 ms    [User: 49.1 ms, System: 8.8 ms]
  Range (min … max):    53.5 ms …  62.2 ms    54 runs

Summary
  'node ./dist-before/corepack.js --version' ran
    1.00 ± 0.05 times faster than 'node ./dist-after/corepack.js --version'

[xiaoxiangmoe]

This PR helps me a lot.

[micsco]

Thanks, @aduh95 - Good catch on the password encoding process.
I've updated both the readme file and the password encoding - I believe that the usual behaviour is just to have the password in plaintext in the environment variables so I have made that so.

[aduh95]

LGTM modulo a few unrelated empty lines that were added probably by accident.

[aduh95]

@micsco it looks like the added test fails:

FAIL tests/npmRegistryUtils.test.ts
  ● npm registry utils fetchAsJson › adds authorization header with basic auth if COREPACK_NPM_USERNAME and COREPACK_NPM_PASSWORD are set
    expect(jest.fn()).lastCalledWith(...expected)
    - Expected
    + Received
      "https://registry.npmjs.org/package-name",
      Object {
        "headers": Object {
          "Accept": "application/vnd.npm.install-v1+json",
    -     "authorization": "Basic am9objplYXN5cGFzczEyMw==",
    +     "authorization": "Basic am9objpqb2hu",
        },
      },
    Number of calls: 1
      73 |
      74 |     expect(httpFetchAsJson).toBeCalled();
    > 75 |     expect(httpFetchAsJson).lastCalledWith(`${DEFAULT_NPM_REGISTRY_URL}/package-name`, {headers: {
         |                             ^
      76 |       ...DEFAULT_HEADERS,
      77 |       authorization: `Basic ${encodedCreds}`,
      78 |     }});
      at Object.lastCalledWith (tests/npmRegistryUtils.test.ts:75:29)

Can you take a look?

[micsco]

@aduh95 apologies, I used the Username env var twice, instead of using the password - thankfully tests caught it but I forgot to check. Have updated the branch.

[merceyz]

Suggested change

	expect(fetchAsJson(`package-name`)).rejects.toThrowError();
	await expect(fetchAsJson(`package-name`)).rejects.toThrowError();

[merceyz]

Could you update the description to mention that this PR Resolves https://github.com/nodejs/corepack/issues/66?

[micsco]

Thanks for the comprehensive review @merceyz - I've applied all your changes and updated the PR.