infobip-api-php-client v3 requires Guzzle ^6.5, incompatible with Guzzle 7

infobip-api-php-client v3 required guzzlehttp/guzzle: ^6.5, so it could not be installed in any project already on Guzzle 7. Users on v2.x who wanted the v3 improvements were stuck waiting.

The maintainers lifted the Guzzle 6 constraint and added Guzzle 7 support, released in version 3.1.0. Upgrade infobip-api-php-client to 3.1.0 or later to use it alongside Guzzle 7.

Source: https://github.com/infobip/infobip-api-php-client/issues/45