deprecate api

Author: Ugonnaak1

msal/application.py

@@ -1815,7 +1815,11 @@ def acquire_token_by_username_password(
             # because this ROPC won't work with MSA account anyway.
             auth_scheme=None,
             **kwargs):
-        """Gets a token for a given resource via user credentials.
+        """
+        [Deprecated] This API is deprecated and will be removed in a future release. Use a more secure flow instead. 
+        Migration guide: https://aka.ms/msalnet-ropc-migration
+        
+        Gets a token for a given resource via user credentials.
 
         See this page for constraints of Username Password Flow.
         https://github.com/AzureAD/microsoft-authentication-library-for-python/wiki/Username-Password-Authentication
@@ -1841,6 +1845,7 @@ def acquire_token_by_username_password(
             - A successful response would contain "access_token" key,
             - an error response would contain "error" and usually "error_description".
         """
+        warnings.warn("This API has been deprecated, please use a more secure flow. See https://aka.ms/msal-ropc-migration for migration guidance", DeprecationWarning)
         claims = _merge_claims_challenge_and_capabilities(
                 self._client_capabilities, claims_challenge)
         if self._enable_broker and sys.platform in ("win32", "darwin"):