fix: add ATLASSIAN_OAUTH_ENABLE to clean_env mock environment (#587)

The test_no_services_configured test was failing because ATLASSIAN_OAUTH_ENABLE
environment variable was not being cleared in MockEnvironment.clean_env().
This caused the get_available_services() function to detect OAuth configuration
even in a supposedly clean environment.

Added ATLASSIAN_OAUTH_ENABLE to the list of variables cleared by clean_env()
to ensure tests run with a truly clean environment.

Author: sooperset

tests/utils/mocks.py

@@ -58,6 +58,7 @@ def clean_env():
             "ATLASSIAN_OAUTH_REDIRECT_URI",
             "ATLASSIAN_OAUTH_SCOPE",
             "ATLASSIAN_OAUTH_CLOUD_ID",
+            "ATLASSIAN_OAUTH_ENABLE",
         ]
 
         # Remove auth vars from environment