Add support for loading configurations values from systemd credentials

cmsmanage/settings.py

@@ -1,3 +1,4 @@
+import os
 from pathlib import Path
 
 from django.core import validators
@@ -8,6 +9,17 @@ BASE_DIR = Path(__file__).resolve().parent.parent
 
 
 class Base(Configuration):
+    @classmethod
+    def pre_setup(cls):
+        super().pre_setup()
+
+        # load systemd credentials, as per https://systemd.io/CREDENTIALS/
+        credentials_directory = os.getenv("CREDENTIALS_DIRECTORY")
+        if credentials_directory is not None:
+            for credential in Path(credentials_directory).iterdir():
+                if credential.name.isupper():
+                    os.environ.setdefault(credential.name, credential.read_text())
+
     @classmethod
     def setup(cls):
         super().setup()