Refactor CLI to more closely reflect Web interface

[samlown]

The current CLI consists of the following principal commands (there are more utility commands):

• build - calculate, validate, and sign a partial GOBL Envelope
• envelope - wrap in an envelope, calculate, validate, and sign a GOBL Document
• verify - validate an envelope and check it was signed with a known signature.

The Web UI however is highlighting a different way to interact with GOBL envelopes and documents which feels a bit more intuitive. The following set of key actions will align both interfaces. All commands output a complete GOBL Envelope, regardless of the input which may be a partial envelope, or a document:

• calculate - Perform calculations only, including invoice totals and envelope header digest.
• validate - Check the contents of the envelope and document look correct (signatures are now optional in GOBL v0.28)
• sign - requires that the envelope is no longer a draft, will calculate, validate and then sign the envelope.

With these set of changes, we can then focus on refining the meaning of the other commands:

• build - performs a calculate and validate, but will not add a signature and works with draft documents.
• envelop - no longer adds any meaning and can be removed.
• verify - should continues as currently, but provide more explicit details on document validation and validity of each of the signatures.

[samlown]

@dstotijn @renegalindo I've tried to refine some of the comments in Slack here. Essentially, the idea is to move to a consistent interface between command line and Web.

[dstotijn]

sign - requires that the envelope is no longer a draft, will validate and then sign the envelope.

You reckon this needs to be a separate command? Or could signing be achieved by using the build command, passing an envelope with head.draft set to false? Or wouldn't that be correct because build always calculates (and sign wouldn't)?

[samlown]

you're right... "build" does seem a bit redundant with these descriptions. Maybe build should just calculate and validate, without a signature, whereas sign does the same and adds the signature, but only for non-drafts... I'll modify the text to see.