Re-implement sorting in API responses

[mileswwatkins]

As of now, it's impossible to sort search endpoints by created_at and similar datetimes. This may have something to do with #49.

[mileswwatkins]

I've set the docs to have no sort abilities for now; this should be fixed accordingly once Imago has it fixed.

[fgregg]

It doesn't seem to be possible to sort by anything:

http://ocd.datamade.us/bills/?from_organization=ocd-organization/ef168607-9135-4177-ad8e-c1f7a4806c3a&sort=identifier

yields

ProgrammingError: SELECT DISTINCT ON expressions must match initial ORDER BY expressions
LINE 1: SELECT COUNT(*) FROM (SELECT DISTINCT ON ("opencivicdata_bil...
                                                  ^

  File "django/core/handlers/base.py", line 149, in get_response
    response = self.process_exception_by_middleware(e, request)
  File "django/core/handlers/base.py", line 147, in get_response
    response = wrapped_callback(request, *callback_args, **callback_kwargs)
  File "django/views/generic/base.py", line 68, in view
    return self.dispatch(request, *args, **kwargs)
  File "django/utils/decorators.py", line 67, in _wrapper
    return bound_func(*args, **kwargs)
  File "django/views/decorators/csrf.py", line 58, in wrapped_view
    return view_func(*args, **kwargs)
  File "django/utils/decorators.py", line 63, in bound_func
    return func.__get__(self, type(self))(*args2, **kwargs2)
  File "restless/views.py", line 106, in dispatch
    response = super(Endpoint, self).dispatch(request, *args, **kwargs)
  File "django/views/generic/base.py", line 88, in dispatch
    return handler(request, *args, **kwargs)
  File "imago/helpers.py", line 137, in _
    return fn(self, request, *args, **kwargs)
  File "imago/helpers.py", line 122, in _
    return fn(self, request, *args, **kwargs)
  File "imago/helpers.py", line 307, in get
    data_page = self.paginate(data, page, per_page)
  File "imago/helpers.py", line 266, in paginate
    return paginator.page(page)
  File "django/core/paginator.py", line 50, in page
    number = self.validate_number(number)
  File "django/core/paginator.py", line 39, in validate_number
    if number > self.num_pages:
  File "django/core/paginator.py", line 86, in _get_num_pages
    if self.count == 0 and not self.allow_empty_first_page:
  File "django/core/paginator.py", line 72, in _get_count
    self._count = self.object_list.count()
  File "django/db/models/query.py", line 371, in count
    return self.query.get_count(using=self.db)
  File "django/db/models/sql/query.py", line 483, in get_count
    number = obj.get_aggregation(using, ['__count'])['__count']
  File "django/db/models/sql/query.py", line 464, in get_aggregation
    result = compiler.execute_sql(SINGLE)
  File "django/db/models/sql/compiler.py", line 852, in execute_sql
    cursor.execute(sql, params)
  File "django/db/backends/utils.py", line 64, in execute
    return self.cursor.execute(sql, params)
  File "django/db/utils.py", line 95, in __exit__
    six.reraise(dj_exc_type, dj_exc_value, traceback)
  File "django/utils/six.py", line 685, in reraise
    raise value.with_traceback(tb)
  File "django/db/backends/utils.py", line 64, in execute
    return self.cursor.execute(sql, params)

Is this the same or a different issue @mileswwatkins

[mileswwatkins]

Hmm, I'm not sure, but I would suspect so. Regardless, fixing one will almost surely fix the other.