JSON parseable error messages

[nelsonwittwer]

Description

Fixes #1033

Please, include a summary of what the PR is for:
As indicated in #1033, our error messages have not been structured in a JSON serializable manner making them very difficult to parse and pass off to the front end to handle.

How has this been tested?

• Unit tests with the expected error data structure
• Pointed at this local branch with a sample CLI created app and verified the errors were JSON parsable:

irb(main):007:0> JSON.parse  "{\"errors\":{\"line_items\":[\"must have at least one line item\"]},\"error_reference\":\"If you report this error, please include this id: 6aa2cdec-9c4f-4f09-8c6d-c059564eacce.\"}"
=> {"errors"=>{"line_items"=>["must have at least one line item"]}, "error_reference"=>"If you report this error, please include this id: 6aa2cdec-9c4f-4f09-8c6d-c059564eacce."}

Checklist:

• My commit message follow the pattern described in here
• I have performed a self-review of my own code.
• I have added tests that prove my fix is effective or that my feature works.
• I have updated the project documentation.
• I have added a changelog line.