Change the API response to return an array of errors

[SargeKhan]

Expected behavior

The API response should return all the errors encountered when processing a request. Therefore, the structure of the API response should be:

{
   "code": 404,
   "error": [{
      message: "<ERROR_MESSAGE>"
   },
   {
      ...
   }]
}

Actual behavior

The structure of API response in case of an error is not very extensible. It contains only one property with the name message which is of type string. In cases where there are multiple errors, it is impossible to return all the errors in this format. The current structure of the API response in case of an error is as follow:

{
   "code": 404,
   "message": "<ERROR_MESSAGE>"
}

Which version(s) does this affect? (Environment, OS, etc...)

1.7

[pablitovicente]

We should also check processUnconfirmedTransaction() in transaction pool as it's only returning one error

[pablitovicente]

We should fix any tests tagged with [feature/improve_transactions_processing_efficiency] on this PR or if scope goes to much up then we should split in different issue blocked by this one

[mitsuaki-u]

We should also check processUnconfirmedTransaction() in transaction pool

Yes that's fixed in the branch I'm working on. I am in the process of updating tests.

[pablitovicente]

@mitsujutsu be aware that PR #3268 fixes integration and some unit tests so you should check that branch (is about to be merged tough)

[mitsuaki-u]

@pablitovicente Ok I am currently working on functional tests so that should not be an issue.