Code cleanup

[darkgl0w]

Hello,

I did a little refresh:

• on test files: explicit test naming and an addition of 2 more test cases
• on plugin code: initialization of fastify.pg and req.pg with Object.create(null) instead of {}, little if.. statements reorganization to fail fast and improve code readability

And I updated this package dependencies too.

Checklist

• run npm run test and npm run benchmark
• tests and/or benchmarks are included
• documentation is changed or added
• commit message and code follows the Developer's Certification of Origin
  and the Code of conduct

[coveralls]

Pull Request Test Coverage Report for Build 1265207839

• 7 of 7 (100.0%) changed or added relevant lines in 1 file are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage remained the same at 100.0%

---

Totals
Change from base Build 1118719299:	0.0%
Covered Lines:	102
Relevant Lines:	102

---

💛 - Coveralls

[coveralls]

Pull Request Test Coverage Report for Build 1265335457

Warning: This coverage report may be inaccurate.

This pull request's base commit is no longer the HEAD commit of its target branch. This means it includes changes from outside the original pull request, including, potentially, unrelated coverage changes.

• For more information on this, see Tracking coverage changes with pull request builds.
• To avoid this issue with future PRs, see these Recommended CI Configurations.
• For a quick fix, rebase this PR at GitHub. Your next report should be accurate.

Details

• 7 of 7 (100.0%) changed or added relevant lines in 1 file are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage remained the same at 100.0%

---

Totals
Change from base Build 1118719299:	0.0%
Covered Lines:	102
Relevant Lines:	102

---

💛 - Coveralls

[mcollina]

Good work, this was much needed! I've left a small note.

[kibertoad]

I'm curious, what is the advantage of this approach?

[darkgl0w]

When we use Object.create(null) we initialize a really empty object that inherit nothing.
Initializing the decorator with {} instead is equivalent to Object.create(Object.prototype) and we have an object that inherit the __proto__ property.
But in fact it can be considered to be just a minor optimization.

[mcollina]

lgtm