feat: support setting headers via env

Author: stainless-app[bot]

src/courier/_client.py

@@ -19,7 +19,11 @@
     RequestOptions,
     not_given,
 )
-from ._utils import is_given, get_async_library
+from ._utils import (
+    is_given,
+    is_mapping_t,
+    get_async_library,
+)
 from ._compat import cached_property
 from ._version import __version__
 from ._streaming import Stream as Stream, AsyncStream as AsyncStream
@@ -119,6 +123,15 @@ def __init__(
         if base_url is None:
             base_url = f"https://api.courier.com"
 
+        custom_headers_env = os.environ.get("COURIER_CUSTOM_HEADERS")
+        if custom_headers_env is not None:
+            parsed: dict[str, str] = {}
+            for line in custom_headers_env.split("\n"):
+                colon = line.find(":")
+                if colon >= 0:
+                    parsed[line[:colon].strip()] = line[colon + 1 :].strip()
+            default_headers = {**parsed, **(default_headers if is_mapping_t(default_headers) else {})}
+
         super().__init__(
             version=__version__,
             base_url=base_url,
@@ -401,6 +414,15 @@ def __init__(
         if base_url is None:
             base_url = f"https://api.courier.com"
 
+        custom_headers_env = os.environ.get("COURIER_CUSTOM_HEADERS")
+        if custom_headers_env is not None:
+            parsed: dict[str, str] = {}
+            for line in custom_headers_env.split("\n"):
+                colon = line.find(":")
+                if colon >= 0:
+                    parsed[line[:colon].strip()] = line[colon + 1 :].strip()
+            default_headers = {**parsed, **(default_headers if is_mapping_t(default_headers) else {})}
+
         super().__init__(
             version=__version__,
             base_url=base_url,