Fix snapshots in aggregate partials

[sonja-turo]

This pull request is an attempted, updated fix for issue #307 where the states of partials are not restored when a snapshot is retrieved.

This update works by defining a single key (default __esPartials) in the event sourcing config file that is used as a key in the state of a snapshot. Each partial is then reflected for public properties, and a key that is the classname of the partial is added to the __esPartials in the generated. The value of that key is the state of the partial.

This will generate a snapshot state of:

$state = [
    'foo' => 'bar',
    '__esPartials' => [
        'App/Partials/FooPartial' => [
            'fooProperty1' => 1,
            'fooProperty2' => true
    ],
];

Reconstitution of the snapshot goes through each key of __esPartials and matches to a resolved Partial Class, and sets the state of that Partials.

[sebastiandedeyne]

Looks good! One thing I'd consider changing is removing the partials key altogether. Slashes can't be used for PHP properties anyway, so there won't be a clash in property names. Might as well keep it flat then.

$state = [
    'foo' => 'bar',
    'App\Partials\FooPartial' => [
        'fooProperty1' => 1,
        'fooProperty2' => true
    ],
];

[sonja-turo]

The unneeded _esPartials key has been removed.

[sonja-turo]

@sebastiandedeyne Just a little bump.

[sebastiandedeyne]

Thanks!