Enable http_client decoration

Author: rayluo

msal/application.py

@@ -20,6 +20,7 @@
 from .token_cache import TokenCache
 import msal.telemetry
 from .region import _detect_region
+from .http_decorate import _decorate
 
 
 # The __init__.py will import this. Not the other way around.
@@ -295,6 +296,7 @@ def __init__(
             a = requests.adapters.HTTPAdapter(max_retries=1)
             self.http_client.mount("http://", a)
             self.http_client.mount("https://", a)
+        _decorate(self.http_client, {})  # Hard code an in-memory cache, for now
 
         self.app_name = app_name
         self.app_version = app_version
@@ -392,6 +394,7 @@ def _build_client(self, client_credential, authority, skip_regional_client=False
             "x-client-sku": "MSAL.Python", "x-client-ver": __version__,
             "x-client-os": sys.platform,
             "x-client-cpu": "x64" if sys.maxsize > 2 ** 32 else "x86",
+            "x-ms-lib-capability": "retry-after, h429",
         }
         if self.app_name:
             default_headers['x-app-name'] = self.app_name