Enhance conference validation and add MAX_CONF_DAYS

- Add checks for conference start and end dates.
- Set maximum conference duration to 20 days.

Closes: #182

agenda/conference.py

@@ -6,8 +6,11 @@ from datetime import date, datetime
 
 import yaml
 
+from . import utils
 from .event import Event
 
+MAX_CONF_DAYS = 20
+
 
 @dataclasses.dataclass
 class Conference:
@@ -55,6 +58,9 @@ def get_list(filepath: str) -> list[Event]:
     """Read conferences from a YAML file and return a list of Event objects."""
     events: list[Event] = []
     for conf in (Conference(**conf) for conf in yaml.safe_load(open(filepath, "r"))):
+        assert conf.start <= conf.end
+        duration = (utils.as_date(conf.end) - utils.as_date(conf.start)).days
+        assert duration < MAX_CONF_DAYS
         event = Event(
             name="conference",
             date=conf.start,