Refactor datetime handling to use UTC throughout

the application

Update datetime handling across the application to consistently utilize
UTC, ensuring uniformity and eliminating potential discrepancies due to
time zone differences.

Author: Mithun Thomas

README.md

@@ -734,7 +734,7 @@ crud_users.update(db=db, object={name="Updated Name"}, username="myusername")
 To delete we have two options:
 - db_delete: actually deletes the row from the database
 - delete: 
-    - adds `"is_deleted": True` and `deleted_at: datetime.now(timezone.utc)` if the model inherits from `PersistentDeletion` (performs a soft delete), but keeps the object in the database.
+    - adds `"is_deleted": True` and `deleted_at: datetime.now(UTC)` if the model inherits from `PersistentDeletion` (performs a soft delete), but keeps the object in the database.
     - actually deletes the row from the database if the model does not inherit from `PersistentDeletion`
 
 ```python

src/app/core/db/models.py

@@ -1,5 +1,5 @@
 import uuid as uuid_pkg
-from datetime import datetime, timezone
+from datetime import datetime, UTC
 from sqlalchemy import Column, DateTime, Boolean, text
 from sqlalchemy.dialects.postgresql import UUID
 
@@ -8,8 +8,8 @@ class UUIDMixin:
 
 
 class TimestampMixin:
-    created_at: datetime = Column(DateTime, default=datetime.now(timezone.utc), server_default=text("current_timestamp(0)"))
-    updated_at: datetime = Column(DateTime, nullable=True, onupdate=datetime.now(timezone.utc), server_default=text("current_timestamp(0)"))
+    created_at: datetime = Column(DateTime, default=datetime.now(UTC), server_default=text("current_timestamp(0)"))
+    updated_at: datetime = Column(DateTime, nullable=True, onupdate=datetime.now(UTC), server_default=text("current_timestamp(0)"))
 
 
 class SoftDeleteMixin:

src/app/core/schemas.py

@@ -1,6 +1,6 @@
 from typing import Any
 import uuid as uuid_pkg
-from datetime import datetime, timezone
+from datetime import datetime, UTC
 
 from pydantic import BaseModel, Field, field_serializer
 
@@ -15,7 +15,7 @@ class UUIDSchema(BaseModel):
 
 
 class TimestampSchema(BaseModel):
-    created_at: datetime = Field(default_factory=lambda:  datetime.now(timezone.utc).replace(tzinfo=None))
+    created_at: datetime = Field(default_factory=lambda:  datetime.now(UTC).replace(tzinfo=None))
     updated_at: datetime = Field(default=None)
 
     @field_serializer("created_at")

src/app/core/security.py

@@ -1,5 +1,5 @@
 from typing import Union, Literal, Dict, Any
-from datetime import datetime, timedelta, timezone
+from datetime import datetime, timedelta, UTC
 
 import bcrypt
 from sqlalchemy.ext.asyncio import AsyncSession
@@ -41,19 +41,19 @@ async def authenticate_user(username_or_email: str, password: str, db: AsyncSess
 async def create_access_token(data: dict[str, Any], expires_delta: timedelta | None = None) -> str:
     to_encode = data.copy()
     if expires_delta:
-        expire = datetime.now(timezone.utc) + expires_delta
+        expire = datetime.now(UTC).replace(tzinfo=None) + expires_delta
     else:
-        expire = datetime.now(timezone.utc) + timedelta(minutes=15)
+        expire = datetime.now(UTC).replace(tzinfo=None) + timedelta(minutes=15)
     to_encode.update({"exp": expire})
     encoded_jwt: str = jwt.encode(to_encode, SECRET_KEY, algorithm=ALGORITHM)
     return encoded_jwt
 
 async def create_refresh_token(data: dict[str, Any], expires_delta: timedelta | None = None) -> str:
     to_encode = data.copy()
     if expires_delta:
-        expire = datetime.now(timezone.utc) + expires_delta
+        expire = datetime.now(UTC).replace(tzinfo=None) + expires_delta
     else:
-        expire = datetime.now(timezone.utc) + timedelta(days=REFRESH_TOKEN_EXPIRE_DAYS)
+        expire = datetime.now(UTC).replace(tzinfo=None) + timedelta(days=REFRESH_TOKEN_EXPIRE_DAYS)
     to_encode.update({"exp": expire})
     encoded_jwt: str = jwt.encode(to_encode, SECRET_KEY, algorithm=ALGORITHM)
     return encoded_jwt

src/app/core/utils/rate_limit.py

@@ -1,4 +1,4 @@
-from datetime import datetime, timezone
+from datetime import datetime, UTC
 
 from redis.asyncio import Redis, ConnectionPool
 from sqlalchemy.ext.asyncio import AsyncSession
@@ -22,7 +22,7 @@ async def is_rate_limited(
         logger.error("Redis client is not initialized.")
         raise Exception("Redis client is not initialized.")
 
-    current_timestamp = int(datetime.now(timezone.utc).timestamp())
+    current_timestamp = int(datetime.now(UTC).timestamp())
     window_start = current_timestamp - (current_timestamp % period)
 
     sanitized_path = sanitize_path(path)

src/app/crud/crud_base.py

@@ -1,5 +1,5 @@
 from typing import Any, Dict, Generic, List, Type, TypeVar, Union
-from datetime import datetime, timezone
+from datetime import datetime, UTC
 
 from pydantic import BaseModel
 from sqlalchemy import select, update, delete, func, and_, inspect
@@ -441,7 +441,7 @@ async def update(
             update_data = object.model_dump(exclude_unset=True)
 
         if "updated_at" in update_data.keys():
-            update_data["updated_at"] = datetime.now(timezone.utc)
+            update_data["updated_at"] = datetime.now(UTC)
 
         stmt = update(self._model) \
             .filter_by(**kwargs) \
@@ -500,7 +500,7 @@ async def delete(
             if "is_deleted" in self._model.__table__.columns:
                 object_dict = {
                     "is_deleted": True,
-                    "deleted_at": datetime.now(timezone.utc)
+                    "deleted_at": datetime.now(UTC)
                 }
                 stmt = update(self._model) \
                     .filter_by(**kwargs) \

src/app/models/tier.py

@@ -1,5 +1,5 @@
 from typing import Optional
-from datetime import datetime, timezone
+from datetime import datetime, UTC
 
 from sqlalchemy import String, DateTime
 from sqlalchemy.orm import Mapped, mapped_column
@@ -15,6 +15,6 @@ class Tier(Base):
     name: Mapped[str] = mapped_column(String, nullable=False, unique=True)
 
     created_at: Mapped[datetime] = mapped_column(
-        DateTime, default_factory=lambda:  datetime.now(timezone.utc).replace(tzinfo=None)
+        DateTime, default_factory=lambda:  datetime.now(UTC).replace(tzinfo=None)
     )
     updated_at: Mapped[Optional[datetime]] = mapped_column(default=None)

src/app/models/user.py

@@ -1,6 +1,6 @@
 from typing import Optional
 import uuid as uuid_pkg
-from datetime import datetime, timezone
+from datetime import datetime, UTC
 
 from sqlalchemy import String, DateTime, ForeignKey
 from sqlalchemy.orm import Mapped, mapped_column
@@ -24,7 +24,7 @@ class User(Base):
         default_factory=uuid_pkg.uuid4, primary_key=True, unique=True
     )
     created_at: Mapped[datetime] = mapped_column(
-        DateTime, default_factory=lambda:  datetime.now(timezone.utc).replace(tzinfo=None)
+        DateTime, default_factory=lambda:  datetime.now(UTC).replace(tzinfo=None)
     )
     updated_at: Mapped[Optional[datetime]] = mapped_column(default=None)
     deleted_at: Mapped[Optional[datetime]] = mapped_column(default=None)

src/scripts/create_first_superuser.py

@@ -13,7 +13,7 @@
 )
 from sqlalchemy.dialects.postgresql import UUID
 import uuid
-from datetime import datetime, timezone
+from datetime import datetime, UTC
 
 from ..app.core.db.database import async_engine
 from ..app.core.db.database import AsyncSession, local_session
@@ -42,7 +42,7 @@ async def create_first_user(session: AsyncSession) -> None:
             Column("hashed_password", String, nullable=False),
             Column("profile_image_url", String, default="https://profileimageurl.com"),
             Column("uuid", UUID(as_uuid=True), primary_key=True, default=uuid.uuid4, unique=True),
-            Column("created_at", DateTime, default=lambda:  datetime.now(timezone.utc).replace(tzinfo=None), nullable=False),
+            Column("created_at", DateTime, default=lambda:  datetime.now(UTC).replace(tzinfo=None), nullable=False),
             Column("updated_at", DateTime),
             Column("deleted_at", DateTime),
             Column("is_deleted", Boolean, default=False, index=True),