Refactor for item display pass1

In a prior email Ralf said:
>>John said
>> So the code re-arrangement would be:
>[...]
>Yes!
>
>> This would unify the representation of the objects regardless of which
>> way they were accessed (class (+ optional embed), class/id (+ optional
>> embed)) for a given verbose level.
>Yes!
>
>> If the property is requested/shown (either by an explicit @embed, or
>> implicitly by requesting the class/id) it always has the exact same
>> form based on the @verbose level.
>Yes!

I took a first pass at it. It passes all the rest tests using anydbm.
It still uses verbose=1 as the default. So we will have to update the
code to use Ralf's new verbose values.

This change adds a new method to the RestfulInstance class:

   def format_item(self, node, item_id, props=None, verbose=1):

The properties included in the output are defined by props. It is a dict
{ propname: proptype } as though returned by

    class_obj.getprops()

If @verbose is set to 2, the labelprop is also included. item_id is a
string and node is the result of a class_obj.getnode(item_id) since
the caller already has one around anyway. This function is basically
the formatting/dict generation part of the /class_name/item_id method.

It turns out that the /class_name/item_id GET handler already supported
@fields to specify returned fields. It was a comma separated list of
field names/properties/attributes. So I made the code support

    @fields=prop1,prop2

and

    @attrs=prop1,prop2

Note ":" can be used in place of ","s, but they can't be mixed. Get
for both /class_name and /class_name/item_id supports @fields/@attrs.
We should probably choose one key and one format (, or :) and remove
the other one. I think @fields makes more sense (and is shorter than
@attributes).

When accessing /class_name/item_id, the results of format_item are
assigned to the "attributes" key of returned dict. When accessing
/class_name the results of format_item are updated/merged into the
dict that is a member of the list "collection".

So:

  rest/data/user?@verbose=2&@attrs=queries:organisation

now returns:

collection": [
   {
       "organisation": null,
       "username": "admin",
       "id": "1",
       "link": ".../rest/data/user/1",
       "queries": [
           {
               "name": "Show Unassigned",
               "id": "4",
               "link": ".../rest/data/query/4"
           }
       ]
   }, ...

while:

  rest/data/user/1?@verbose=2&@fields=queries,organisation returns:

{   
  "data": {
    "attributes": {
      "organisation": null,
      "queries": [
        {  
          "link": ".../rest/data/query/4",
          "name": "Show Unassigned",
          "id": "4"
        }
      ],
      "username": "admin"
    },
    "@etag": "\"a3d16094da6c6de1c1e9fe56a1ff763d\"",
    "link": ".../rest/data/user/1",
    "type": "user",
    "id": "1"
  }
}

Same queries but with @verbose=0 for /class_name returns:

  "collection": [
      {
          "organisation": null,
          "link": "https://rouilj.dynamic-dns.net/demo/rest/data/user/1",
          "queries": [
              "4"
          ],
          "id": "1"
      }, ...

and for /class_name/item_id:

{   
    "data": {
        "attributes": {
            "organisation": null,
            "queries": [
                "4"
            ]
        },
        "@etag": "\"a3d16094da6c6de1c1e9fe56a1ff763d\"",
        "link": "https://rouilj.dynamic-dns.net/demo/rest/data/user/1",
        "type": "user",
        "id": "1"
    }
}

Also this code doesn't display password fields. Instead it displays:

   "password": "[password hidden scheme PBKDF2]",

if the scheme is PBKDF2 or the account it locked without a password.
 
This can probably be optimized and cleaned up but I think it's ok for
a first pass.

I'll try to get a test or two in for @fields, @attrs and different
@verbose levels this weekend.

Have a great weekend all.

--
				-- rouilj
John Rouillard
===========================================================================
My employers don't acknowledge my existence much less my opinions.