Declare strict types

[JaZo]

Description

I've declared strict types in all classes and also configured PHP-CS-Fixer to make it required.

Motivation and context

To improve code quality and reduce errors.

N.B. Sometimes an id is provided as integer and we don't want to break on that small detail, so I cast them to a string before setting them on the item. Since the type declaration of the id was already a string the output won't change.

How has this been tested?

Tested in a real life application.

Types of changes

What types of changes does your code introduce? Put an x in all the boxes that apply:

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)

N.B. Declaring strict types can be considered a breaking change, but since we already have strict type checks in our parsers and I added the cast for the ID's, I believe the vast majority of users will not be affected.

Checklist:

Go over all the following points, and put an x in all the boxes that apply.

• I have read the CONTRIBUTING document.
• My pull request addresses exactly one patch/feature.
• I have created a branch for this patch/feature.
• Each individual commit in the pull request is meaningful.
• I have added tests to cover my changes.
• If my change requires a change to the documentation, I have updated it accordingly.

[Rocksheep]

Looks good to me! I have run a couple of examples and didn't receive an error. 👍