Added guzzlehttp/psr7 as dev dependency for tests

Author: joelbutcher

composer.json

@@ -24,6 +24,7 @@
         "psr/http-message": "^1.0"
     },
     "require-dev": {
+        "guzzlehttp/psr7": "^2.0",
         "mockery/mockery": "^1.0",
         "php-http/guzzle6-adapter": "^1.0",
         "phpunit/phpunit": "^9.3"