fix: throw 'not implemented' error in buildDepTree for npm v2/v3 lockfiles

[milahu]

• [ ] Tests written and linted
• [ ] Documentation written / README.md updated https://snyk.io/docs/snyk-for-node/
• [ ] Follows CONTRIBUTING agreement
• [ ] Commit history is tidy https://git-scm.com/book/en/v2/Git-Branching-Rebasing
• [ ] Reviewed by Snyk team

What this does

throw not implemented error in buildDepTree for npm v2/v3 lockfiles

better than OutOfSyncError from getDependencyTree

OutOfSyncError: Dependency @cycle/http was not found in package-lock.json. Your package.json and package-lock.json are probably out of sync. Please run "npm install" and try again.
    at PackageLockParser.getDependencyTree (node_modules/snyk-nodejs-lockfile-parser/dist/parsers/lock-parser-base.js:124:27)
    at async PackageLockParser.getDependencyTree (node_modules/snyk-nodejs-lockfile-parser/dist/parsers/package-lock-parser.js:28:32)
  code: 422,
  dependencyName: '@cycle/http',
  lockFileType: 'npm7'

problem in PackageLockParser.getDepMap: packageLock.dependencies is undefined, it should use packageLock.packages

https://github.com/snyk/nodejs-lockfile-parser/blob/103bb2de2e8391fab2b35c57e8c64b14e8205e3e/lib/parsers/package-lock-parser.ts#L110

so the not implemented error is thrown in getDepMap before calling flattenLockfileRec

to implement support for v2/v3 npm lockfiles, a good place would be getDepMap

  protected getDepMapV2(packageLock: PackageLock): DepMap {
    // TODO implement
  }

  protected getDepMap(lockfile: Lockfile): DepMap {
    const packageLock = lockfile as PackageLock;

    if (packageLock.lockfileVersion == 2) {
      return this.getDepMapV2(packageLock);
    }

Notes for the reviewer

low priority