Implement EventID to scope ClientIDs and Entry IDs

Implement an EventID saved in settings. Currently this is used to scope
clientIDs and entryIDs to an event. The client checks the event currently going on on
the server, and discards its localstorage (containing the clientID) if
it has changed

backend/helpers.py

@@ -98,6 +98,7 @@ def setup_config(app: Flask):
         for key, value in default_config.items():
             database.set_config(key, value)
         print("Created new config")
+        database.init_event_id()
     config = database.get_config_list()
     app.config['BASIC_AUTH_USERNAME'] = config['username']
     app.config['BASIC_AUTH_PASSWORD'] = config['password']
@@ -105,6 +106,7 @@ def setup_config(app: Flask):
     app.config['MAX_QUEUE'] = config['maxqueue']
     app.config['ENTRIES_ALLOWED'] = bool(config['entries_allowed'])
     app.config['THEME'] = config['theme']
+    app.config['EVENT_ID'] = database.get_event_id()
 
 # set queue admittance
 
@@ -153,6 +155,15 @@ def set_theme(app: Flask, theme: str):
         print("Theme not found, not setting theme.")
 
 
+def get_current_event_id(app: Flask):
+    return app.config['EVENT_ID']
+
+
+def reset_current_event_id(app: Flask):
+    database.reset_event_id()
+    app.config['EVENT_ID'] = database.get_event_id()
+
+
 def nocache(view):
     @wraps(view)
     def no_cache(*args, **kwargs):