Denormalising users shouldn't call save on edition

www.agileplannerapp.com/boards/173808/cards/4296

Denormalising users is a process that's setting
values for a few columns, which doesn't need the
the entire validation chain or callbacks to
execute. there are no validations related to
denormalisation, all the more reason for it
to be a plain #set.

there's a cost involved here of multiple
update queries being fired, but that should
be substantially lower than triggering callbacks
and validation chain repeatedly.
Merge pull request #186 from alphagov/save-without-validation-for-denormalisation

Denormalising users shouldn't need save on edition
Release 13.2.0

www.agileplannerapp.com/boards/173808/cards/4296

Denormalising users doesn't require the entire edition
to be validated and saved. Hence replacing it with a
set operation.
Assigning an edition doesn't require save

assignment updates the `assigned_to_id` on a edition
and doesn't require the entire validation and callback
chain to get executed.
Merge pull request #187 from alphagov/assignment-doesnt-need-a-save

Assigning an edition doesn't require save
Add AAIB & CMA to app ownership const

Add aaib-report and cma-case to the FORMATS_BY_DEFAULT_OWNING_APP constant. This will allow us to key of this in apps which consume the api rather than surfacing the document_type for all artefacts
Validate slug for all SpecialistDocument types

..not just the one with a format of specialist-document. Since we have now introduced more types of document lets pull the document types from the FORMATS_BY_DEFAULT_OWNING_APP mappings and remove the ones we don't need.