Started working on events/activities based on Florians work

src/fiber_package/events/activity.py

@@ -0,0 +1,25 @@
+from typing import Annotated, Self
+
+from .communication import CommunicationModel
+
+class ActivityModel(CommunicationModel):
+    category: Annotated[
+        CommunicationCategory,
+        Field(pattern=CommunicationCategory.activity)
+    ]
+
+    start_time: datetime
+    end_time: datetime
+
+
+    #signuplist: GroupRef | None = None
+    # TODO: implement signup list (huge modular system)
+
+    # TODO: see Felt 'activiteiten' DB schema. Things like:
+    # costs, payment method, email, target group, maximal attendees ....
+
+    @model_validator(mode='after')
+    def check_end_after_start(self) -> Self:
+        if self.end_time < self.start_time:
+            raise ValueError("End time cannot be earlier than start time")
+        return self

src/fiber_package/events/communication.py

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+from pydantic import BaseModel, model_validator, Field, HttpUrl
+from enum import StrEnum
+from datetime import datetime
+
+from fiber_package.base import FiberBaseModel
+
+from .enums import CommunicationCategory
+
+'''
+A "communication" is a piece of communication/promotion to be shared with
+members, which may appear on the website and in the weekly mailing.
+'''
+class CommunicationModel(FiberBaseModel):
+    category: CommunicationCategory
+
+    name_en: str
+    name_nl: str
+
+    association_tags = []
+    # list of associations this communication belongs to
+
+    subtitle_en: str
+    subtitle_nl: str
+    # subtitles currently (2026) appear only in the table of contents in the
+    # weekly mailing; they are meant to be a short catchy flavour text
+
+    description_en: str
+    description_nl: str
+
+    image: HttpUrl | None = None
+    # often, a poster comes associated with a communication (in particular if
+    # it's an activity). In that case, the poster is uploaded to the cloud and
+    # the share link is attached to the communication
+    # TODO: potentially rethink the way images are attached to communications
+
+    visibility: bool
+    # should this communication be shown to members at all? Useful for
+    # temporarily hiding a communication
+    
+    only_members: bool
+    # is this communication only visible to members? This refers to visibility
+    # on the website, i.e. is this only visible to visitors who are logged in?
+    
+    archived: bool
+    # an archived communication cannot be edited, only viewed for future
+    # reference

src/fiber_package/events/enums.py

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+from enum import StrEnum
+
+'''
+The category is only used to place the communication correctly in the weekly
+mailing and the board-website, it is not visible (or relevant) to readers
+'''
+class CommunicationCategory(StrEnum):
+    announcement = "announcement"
+    news = "news"
+    activity = "activity"