libs: add contentType as optional options

Author: hex7c0

composer.json

@@ -18,9 +18,9 @@
     "queue-interop/amqp-interop": "0.8.*"
   },
   "require-dev": {
-    "phpunit/phpunit": "^7.0",
+    "phpunit/phpunit": "7.5.*",
     "illuminate/events": "5.8.*",
-    "mockery/mockery": "^1.0"
+    "mockery/mockery": "1.3.*"
   },
   "autoload": {
     "psr-4": {