Add psr/http-message as composer Dependency for ILIAS 12

[thibsy]

Assessment:

General Information:

• Name of the dependency: psr/http-message
• Version: 2.0
• this dependency was already used in ILIAS.
• the dependency's license is compatible with ILIAS' license: MIT

Type of dependency:

• composer
• npm

Usage:

• components/ILIAS/HTTP
• components/ILIAS/UI
• (many other components)`

Reasoning:

• Our codebase already heavily relies on the PSR-7 HTTP message interfaces.
• Adding the package explicitly makes this requirement clear and prevents possible issues that arise when depending on a transitive dependency.
• The message interfaces are the de-facto standard for working with HTTP in PHP.

Maintenance:

• Last update of the Library: 2023-04-04, PHP Version: ^7.2 || ^8.0

Links:

• Packagist: https://packagist.org/packages/psr/http-message
• GitHub: https://github.com/php-fig/http-message.git
• Documentation: https://github.com/php-fig/http-message

Alternatives:

• Framework-specific abstractions (e.g., Symfony, Guzzle)

[matthiaskunkel]

Jour Fixe, 08 DEC 2025: Dependency is accepted for ILIAS 12.

[lscharmer]

Merged with PR: #11255