fix: compatibility with new version of guzzle (guzzle > 5.3.0 & PHP >= 8)

[emanuelgomez-s1]

This PR addresses a compatibility issue in the Google\Http\REST class related to legacy support for GuzzleHttp\Message\ResponseInterface, which was removed in Guzzle 6+. The existing code conditionally checks for this obsolete interface and attempts to convert responses, but this behavior is unnecessary (and potentially problematic) in modern environments using Guzzle >=6 and PHP 8.

The proposed change removes this outdated compatibility layer and ensures cleaner, future-proof code that aligns.

Thanks for your cooperation @macatapichon

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[bshaffer]

This class is using Psr\Http\Message\ResponseInterface, and not GuzzleHttp\Message\ResponseInterface, so I'm not sure what problem is being solved here. Perhaps you can write a test or provide a code example?

[emanuelgomez-s1]

Hi @bshaffer, thanks for the feedback!

The issue I'm addressing occurs when using "google/apiclient": "^2.9" together with "guzzlehttp/guzzle": "^7.0.1" and PHP 8. In this setup, I'm encountering a critical runtime error because the \GuzzleHttp\Message\ResponseInterface interface no longer exists in Guzzle 6+:

Error: Failed opening required '/efs/apps/XXX/model/GuzzleHttp/Message/ResponseInterface.php' (include_path='.:/usr/share/php')

This stems from the condition in REST::doExecute():

if (
    interface_exists('\GuzzleHttp\Message\ResponseInterface')
    && $response instanceof \GuzzleHttp\Message\ResponseInterface
)

Even though the class is primarily working with Psr\Http\Message\ResponseInterface, the fallback to \GuzzleHttp\Message\ResponseInterface is what causes the issue on newer setups. Since older versions of Guzzle (e.g., 5.x) are not compatible with PHP 8, referencing interfaces from those versions causes fatal errors in modern environments. My patch updates the condition to a safer and more compatible approach:

if ($response instanceof ResponseInterface && !($response instanceof Response))

This avoids referencing a non-existent interface and maintains compatibility with PSR-7 responses.

Let me know if you'd like me to add a test or more context