feat: Implement middleware for schema validations

[LautaroPetaccio]

This PR implements a middleware to do request body validations.
Each request is validated through a request schema and, in case of errors, the response is formatted as it was done before, with the exception of the status code that now is a 400 (bad request).

[coveralls]

Pull Request Test Coverage Report for Build 1337379287

• 12 of 12 (100.0%) changed or added relevant lines in 4 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage increased (+0.1%) to 55.28%

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Totals
Change from base Build 1321564241:	0.1%
Covered Lines:	1323
Relevant Lines:	2205

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💛 - Coveralls

[fzavalia]

This is great. We can now remove all the validations that were handled directly by the request handler function and there was a lot repeated

[fzavalia]

Should't you just throw the error as it was done inside the handlers?
Example from items router

if (validate.errors) {
      throw new HTTPError('Invalid schema', validate.errors)
}

[LautaroPetaccio]

You can do both! Express has a try-catch surrounding handlers that will execute next(error) on error, but it is also possible to use next with the error in your middleware and it will go straight to the error handle middleware.

[fzavalia]

LGTM! question is just out of curiosity