[Improvement]: Replace == with === in PHP comparisons where possible

[solverat]

Improvement description

To improve type safety and prevent unexpected behavior caused by PHP's loose comparisons, we should replace the equality operator == with the strict equality operator === wherever possible.

• Identify occurrences of == in the codebase.
• Replace them with === where it is safe to do so.
• Start with string comparisons, as these are usually the easiest and safest to convert.

Step 1: Strings (Easy)

• https://github.com/search?q=repo%3Aopen-dxp%2Fopendxp++%22+%3D%3D+%27%22&type=code

Step 2: Everything else (Hard)

• https://github.com/search?q=repo%3Aopen-dxp%2Fopendxp++%22+%3D%3D+%27%22&type=code