Update setter's phpdoc return - ApiProblem to $this

[sasezaki]

Description

Updated PHPDoc return type annotations from ApiProblem to $this for fluent interface methods.

The change affects five setter methods:

• setTitle()
• setType()
• setDetail()
• setInstance()
• setStatus()

Motivation and context

This change improves type inference accuracy in IDEs and static analysis tools for subclass ApiProblem.

class MySubApiProblem extends ApiProblem
{
     /** @return $this */
    public function some()
    {
        // do something
        return $this;
    }
}

(new MySubApiProblem)
 ->setTitle($title)
 ->some()  // static analysis would report error
 ->setStatus();

How has this been tested?

• This is a documentation-only change that does not affect runtime behavior:

• I confirmed that the number of errors did not increase when running PHPStan.

./vendor/bin/phpstan analyse
./vendor/bin/phpstan analyse --level=8 // 20 errors
./vendor/bin/phpstan analyse --level=10 // 61 errors

Screenshots (if appropriate)

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)

Checklist:

• 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 it is needed to add new type test (eg. PHPStan's assertType) , I would add.
• If my change requires a change to the documentation, I have updated it accordingly.

[Crell]

Thanks!