fix(RouterStore): serialize routeConfig inside the default serializer

[timdeschryver]

PR Checklist

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• The commit message follows our guidelines: https://github.com/ngrx/platform/blob/master/CONTRIBUTING.md#commit
• Tests for the changes have been added (for bug fixes / features)
• Docs have been added / updated (for bug fixes / features)

PR Type

What kind of change does this PR introduce?

[x] Bugfix
[ ] Feature
[ ] Code style update (formatting, local variables)
[ ] Refactoring (no functional changes, no api changes)
[ ] Build related changes
[ ] CI related changes
[ ] Documentation content changes
[ ] Other... Please describe:

What is the current behavior?

The routeConfig isn't being serialized in DefaultRouterStateSerializer.

Issue Number: #1363

What is the new behavior?

The routeConfig is being serialized in DefaultRouterStateSerializer.
Note that not all properies are being serialized:

{
    // was already being serialized
    component?: Type<any>;

	// added properties to be serialized
    path?: string;
    pathMatch?: string;   
    redirectTo?: string;
    outlet?: string;

    // not being serialized
    matcher?: UrlMatcher;  
    canActivate?: any[];
    canActivateChild?: any[];
    canDeactivate?: any[];
    canLoad?: any[];
    data?: Data;
    resolve?: ResolveData;
    children?: Routes;
    loadChildren?: LoadChildren;
    runGuardsAndResolvers?: RunGuardsAndResolvers;
}

Does this PR introduce a breaking change?

[x] Yes
[ ] No

The default router serializer now returns a null value for routeConfig when routeConfig doesn't exist on the ActivatedRouteSnapshot instead of an empty object.
BEFORE:

{
 "routeConfig": {}
}

AFTER:

{
 "routeConfig": null
}

Other information

If this doesn't belong in the default serializer, feel free to close.
It's always possible for the impacted users to create there own serializer.

Closes #1363

[brandonroberts]

Shouldn't the routeConfig remain an empty object if its not defined to keep the existing behavior?

[timdeschryver]

I initially wanted to do this, but the Angular docs defines it as Route | null.
I wanted to stay as close as possible to this.

I should've payed more attention to when this... because this means that this is a breaking change.

What do you think of it? Should I change this to an empty object or flag this as a breaking change and add it to the migration log?

[brandonroberts]

Flag is as a breaking change. I'd rather the behavior be consistent and this would be the time to break it.

[timdeschryver]

Something like this? I have some troubles to properly word this.

[brandonroberts]

👍

[coveralls]

Coverage decreased (-0.07%) to 88.371% when pulling 92ab3bd on pr/serialeze-routeconfig into 0e38673 on master.