Fix token caching

Dockerfile

@@ -7,8 +7,9 @@ WORKDIR /app
 # Copy the current directory contents into the container at /app
 COPY ./propedal-planner /app
 
-# Install any needed packages specified in requirements.txt
-RUN pip install -r requirements.txt
+# Install any needed packages specified in requirements.txt -use cache
+RUN --mount=type=cache,target=/root/.cache \
+    pip install -r requirements.txt
 
 # Make port available to the world outside this container
 EXPOSE 8001

propedal-planner/calendar_interface.py

@@ -30,16 +30,17 @@ app = msal.ConfidentialClientApplication(
                     # You can learn how to use SerializableTokenCache from
                     # https:#msal-python.readthedocs.io/en/latest/#msal.SerializableTokenCache
     )
+accounts = app.get_accounts(username=None)
 
 def get_access_token():
-    global app, token
+    global app, token, accounts
 
     # The pattern to acquire a token looks like this.
 
     # Firstly, looks up a token from cache
     # Since we are looking for token for the current app, NOT for an end user,
     # notice we give account parameter as None.
-    token = app.acquire_token_silent(MsalConfig.SCOPE, account=None)
+    token = app.acquire_token_silent(MsalConfig.SCOPE, account=accounts[0])
 
     if token is None:
         logging.info("No suitable token exists in cache. Let's get a new one from AAD.")