Neweb APIs overview

• Issue an invoice
• Issue an existed invoice
• Query invoices
• Cancel an invoice
• Allowance of an invoice
• Cancel allowance of an invoice
• Branch Track(?)

Proposal

Now there's only :invalid to leverage with project default ActiveModel i18n. I think there should be provider based i18n.

Approach

• A locale folder contains multiple(probably zh-tw only lol) language i18n files
• Every validation should have its own message

Now the digest_neweb is embed in connection.rb, but it should be a problem when there comes another provider and without using digest like Neweb.

See: https://github.com/abookyun/einvoice/blob/master/lib/einvoice/connection.rb#L15

Wish you a happy lunar new year.
As there're already few commits since the last version, how about cutting a first new release for 2021?

Purpose

• Provide overview of every APIs purpose and how it work
• Provide a clear and updated docs describing why and how validations works.
• Provide why and how result will be success or failure.