Add CRUD operations and tests for Event model

This commit introduces a new CRUDEvent class to manage event-related database operations, including retrieval, creation, updating, and deletion of events. It includes corresponding unit tests to ensure the correctness of these functionalities, updates event schemas for enhanced validation, and refines timezone handling for event dates and deadlines.

backend/app/schemas/events.py

@@ -1,8 +1,8 @@
 from datetime import datetime, time, timezone
-from typing import Dict, Optional, List, Union
+from typing import Dict, Optional
 from uuid import UUID
+
 from pydantic import BaseModel, Field, field_validator
-from zoneinfo import ZoneInfo
 
 
 class EventBase(BaseModel):
@@ -31,6 +31,7 @@ class EventBase(BaseModel):
 
     @field_validator('timezone')
     def validate_timezone(cls, v):
+        from zoneinfo import ZoneInfo
         try:
             ZoneInfo(v)
             return v
@@ -39,15 +40,21 @@ class EventBase(BaseModel):
 
     @field_validator('event_date')
     def validate_event_date(cls, v):
-        if v < datetime.now(tz=timezone.utc):
+        if not v.tzinfo:
+            raise ValueError("Event date must be timezone-aware")
+        now = datetime.now(tz=timezone.utc)
+        if v < now:
             raise ValueError("Event date cannot be in the past")
         return v
 
     @field_validator('rsvp_deadline')
     def validate_rsvp_deadline(cls, v, values):
-        if v and 'event_date' in values.data:
-            if v > values.data['event_date']:
-                raise ValueError("RSVP deadline must be before event date")
+        if v:
+            if not v.tzinfo:
+                raise ValueError("RSVP deadline must be timezone-aware")
+            if 'event_date' in values.data:
+                if v > values.data['event_date']:
+                    raise ValueError("RSVP deadline must be before event date")
         return v