Add support for env variable JUDGE0_SUPPRESS_PREVIEW_WARNING. (#19)

* Add support for env variable JUDGE0_SUPPRESS_PREVIEW_WARNING.

* Minor change to preview warning suppression logic

---------

Co-authored-by: Filip Karlo Došilović <filipk.dosilovic@gmail.com>

Author: hermanzdosilovic

src/judge0/__init__.py

@@ -65,6 +65,7 @@
 
 JUDGE0_IMPLICIT_CE_CLIENT = None
 JUDGE0_IMPLICIT_EXTRA_CE_CLIENT = None
+SUPPRESS_PREVIEW_WARNING = os.getenv("JUDGE0_SUPPRESS_PREVIEW_WARNING")
 
 logger = logging.getLogger(__name__)
 
@@ -106,11 +107,12 @@ def _get_implicit_client(flavor: Flavor) -> Client:
 
 
 def _get_preview_client(flavor: Flavor) -> Union[Judge0CloudCE, Judge0CloudExtraCE]:
-    logger.warning(
-        "You are using a preview version of the client which is not recommended"
-        " for production.\n"
-        "For production, please specify your API key in the environment variable."
-    )
+    if SUPPRESS_PREVIEW_WARNING is not None:
+        logger.warning(
+            "You are using a preview version of the client which is not recommended"
+            " for production.\n"
+            "For production, please specify your API key in the environment variable."
+        )
 
     if flavor == Flavor.CE:
         return Judge0CloudCE()