Add HTTP proxy support via environment variables

When HTTPS_PROXY, https_proxy, HTTP_PROXY, or http_proxy environment
variables are set, use urllib3.ProxyManager instead of PoolManager.

This enables the client to work in environments that require proxy
configuration, such as corporate networks, CI/CD pipelines, and
sandboxed development environments.

The behavior is backward compatible - when no proxy environment
variables are set, PoolManager is used as before.

Author: kevinchiu

massive/rest/base.py

@@ -1,5 +1,6 @@
 import certifi
 import json
+import os
 import urllib3
 import inspect
 from urllib3.util.retry import Retry
@@ -70,14 +71,22 @@ def __init__(
 
         # https://urllib3.readthedocs.io/en/stable/reference/urllib3.poolmanager.html
         # https://urllib3.readthedocs.io/en/stable/reference/urllib3.connectionpool.html#urllib3.HTTPConnectionPool
-        self.client = urllib3.PoolManager(
+        pool_kwargs = dict(
             num_pools=num_pools,
             headers=self.headers,  # default headers sent with each request.
             ca_certs=certifi.where(),
             cert_reqs="CERT_REQUIRED",
             retries=retry_strategy,  # use the customized Retry instance
         )
 
+        # Check for proxy environment variables (HTTPS_PROXY or HTTP_PROXY)
+        proxy_url = os.environ.get("HTTPS_PROXY") or os.environ.get("https_proxy") \
+                    or os.environ.get("HTTP_PROXY") or os.environ.get("http_proxy")
+        if proxy_url:
+            self.client = urllib3.ProxyManager(proxy_url, **pool_kwargs)
+        else:
+            self.client = urllib3.PoolManager(**pool_kwargs)
+
         self.timeout = urllib3.Timeout(connect=connect_timeout, read=read_timeout)
 
         if verbose: