Deprecate `Option.get_(add|change|delete)_permission`.

[Simon Charette]

In the whole Clean Model Options process we should deprecate those methods in favor of contrib.auth alternatives.

Even if those methods are undocumented it's no secret they are used in the wild. Django exclusively use them in contrib.admin:

(django)simon@simon-laptop:~/workspace/django$ grep -E "get_(add|change|delete)_permission" django/ -Rn --include="*.py"
django/db/models/options.py:416:    def get_add_permission(self):
django/db/models/options.py:419:    def get_change_permission(self):
django/db/models/options.py:422:    def get_delete_permission(self):
django/contrib/admin/options.py:355:        return request.user.has_perm(opts.app_label + '.' + opts.get_add_permission())
django/contrib/admin/options.py:369:        return request.user.has_perm(opts.app_label + '.' + opts.get_change_permission())
django/contrib/admin/options.py:383:        return request.user.has_perm(opts.app_label + '.' + opts.get_delete_permission())
django/contrib/admin/options.py:1671:            self.opts.app_label + '.' + self.opts.get_add_permission())
django/contrib/admin/options.py:1683:            opts.app_label + '.' + opts.get_change_permission())
django/contrib/admin/options.py:1693:            self.opts.app_label + '.' + self.opts.get_delete_permission())
django/contrib/admin/util.py:122:                           opts.get_delete_permission())

[Simon Charette]

Added a patch that deprecates option permission methods and moves contrib.auth.management._get_permission_codename to contrib.auth.get_permission_codename and use it in contrib.admin.

Wondering if we should document get_permission_codename, it feels a bit odd to deprecate those methods while specifying no alternatives in the release notes.

I still pointed to it in the raised deprecation warning.

[loic84]

+1 much needed cleanup.

Tested it on a project that uses permissions and ModelAdmin.has_x_permission overrides extensively and didn't notice any issue.

[Simon Charette]

Patch with doc

[Simon Charette]

Updated the RFC patch to use super in InlineAdmin instead of duplicating permission codename creation.

[Simon Charette <charette.s@…>]

In b91787910c9d5a036674d46a73d1b48ca33123a3:

Fixed #20642 -- Deprecated Option.get_(add|change|delete)_permission.

Those methods were only used by contrib.admin internally and exclusively
related to contrib.auth. Since they were undocumented but used
in the wild the raised deprecation warning point to an also undocumented
alternative that lives in contrib.auth.

Also did some PEP8 and other cleanups in the affected modules.

[Simon Charette <charette.s@…>]

In e1dd24d2f6dd3464ab50593320a7eb2325d6c196:

Added missing deprecation note for model permission methods.

refs #20642.

[Simon Charette <charette.s@…>]

In e628753e7dd1611fb4cf770a78126e96a02ab1d7:

[1.6.x] Added missing deprecation note for model permission methods.

refs #20642.

Backport of e1dd24d2f from master.

[Tim Graham <timograham@…>]

In a6a905c619e48bb3db4a5fbb09e5e03abb7ed0f6:

Updated tests for deprecation of Option.get_(add|change|delete)_permission.

refs #20642.

[Tim Graham <timograham@…>]

In 3c51962cabc9537221b86c667aac5ffaa1469660:

[1.6.x] Updated tests for deprecation of Option.get_(add|change|delete)_permission.

refs #20642.

Backport of a6a905c619 from master.