Pick a simpler form framework

[sebbacon]

The current formalchemy setup conflates view, controller and model code in a way that makes it hard to debug and customise.

Review existing (and potentially non-existing) frameworks with a view to porting forms over to something more explicit and lightweight.

Implement the current Package forms as an example of how this would work.

Document and circulate.

Sub-ticket of #961 (form, validation, model sync meta-ticket)

[rgrp]

Comments from RP - ​http://lists.okfn.org/pipermail/ckan-dev/2011-January/000181.html

Libraries I have used: FormEncode?, FormAlchemy? (what we are currently using, before that formencode).

Neither seemed perfect but I think the form issue is a 'hard' problem (perhaps with no perfect answer) [1]. FormAlchemy?, in retrospect, was probably a mistake as it merges too much model/validation/form generation into one thing.

At least 3 functions involved:

1. Generating (or just filling) a form template with 'form data' (and errors)
2. Converting model data to form data (also happens for APIs in fact) -- let's call this 'dict-ization'
3. Converting form data to model data (and validating) (inverse of

previous step)

I think one can and should separate 1 from 2+3 (and one of problems with formalchemy is it doesn't -- the attraction being you don't repeat yourself as forms get generated from model but I think this is actually a false economy in medium-term).

I'm not specifically recommending the following as I haven't used them but I've looked through docs, they are active and reasonably mature:

1. Flatland: ​http://discorporate.us/projects/flatland/docs/tip/
   • Only does 2+3 which is a good thing IMO

2. WTForms: ​http://wtforms.simplecodes.com/
   • Used in standard flask docs: <​http://flask.pocoo.org/docs/patterns/wtforms/>