fix: use ServerZone class for remote evaluation server_zone config

Author: tyiuhc

src/amplitude_experiment/remote/config.py

@@ -1,3 +1,5 @@
+from src.amplitude_experiment import ServerZone
+
 DEFAULT_SERVER_URL = 'https://api.lab.amplitude.com'
 EU_SERVER_URL = 'https://api.lab.eu.amplitude.com'
 
@@ -12,7 +14,7 @@ def __init__(self, debug=False,
                  fetch_retry_backoff_max_millis=10000,
                  fetch_retry_backoff_scalar=1.5,
                  fetch_retry_timeout_millis=10000,
-                 server_zone='us'):
+                 server_zone: ServerZone = ServerZone.US):
         """
         Initialize a config
             Parameters:
@@ -41,6 +43,6 @@ def __init__(self, debug=False,
         self.fetch_retry_backoff_scalar = fetch_retry_backoff_scalar
         self.fetch_retry_timeout_millis = fetch_retry_timeout_millis
         self.server_zone = server_zone
-        if server_url == DEFAULT_SERVER_URL and server_zone == 'eu':
+        if server_url == DEFAULT_SERVER_URL and server_zone == ServerZone.EU:
             self.server_url = EU_SERVER_URL