Add callable support to ModelAwareTrait::loadModel()

[jadb]

This change makes it simpler to create one-off factories by just
doing:

$controller->loadModel(null, ['Cake\ElasticSearch\TypeRegistry', 'get']);

for example or just any anonymous function.

[markstory]

Why wouldn't you directly call the factory if you already have a callable and rhe model name?

[jadb]

In abstracted libraries (i.e. Crud) you don't. This allows to change:

$this->modelFactory('Type', ['Cake\ElasticSearch\TypeRegistry', 'get']);
$this->Crud->action($this->request->param('action'))->config('modelFactory', 'Type');

by:

$this->Crud->action($this->request->param('action'))
            ->config('modelFactory', ['Cake\ElasticSearch\TypeRegistry', 'get']);

or in some cases, using anonymous functions:

$controller->loadModel(null, function() {
    // do something
    return $repository;
});

[markstory]

Couldn't those callers know they are getting a callablr and directly invoke it? I guess my hesitation is that in this mode loadModel() is just indirection. The callable isn't used later on or ever again.

[jadb]

Hmm, I see the point you are making - don't really have arguments against it. If you guys don't think it should be part of the core, I'm fine with that, just saw an opportunity to write even less code and thought it be suggested ;)

[markstory]

@jadb I'm not saying its a bad idea, I just don't think adding a wrapper around calling a function is overly valuable.