feat(db): add message and chat schemas for input/output

Add Pydantic schemas for message and chat models including create, read and update operations. Includes relationships between chat and message models.

db/schemas/chat.py

@@ -0,0 +1,37 @@
+import uuid
+from datetime import datetime
+from typing import Optional
+from pydantic import BaseModel, Field
+
+from .message import MessageRead
+
+# -------------------
+# SCHEMAS FOR INPUT
+# -------------------
+class ChatBase(BaseModel):
+    title: Optional[str] = None
+
+# Properties to receive on creation
+class ChatCreate(ChatBase):
+    title: str
+
+# Properties to receive on update
+class ChatUpdate(ChatBase):
+    title: str
+
+# -------------------
+# SCHEMAS FOR OUTPUT
+# -------------------
+# Schema for listing chats in a sidebar
+class ChatReadSimple(BaseModel):
+    id: uuid.UUID
+    title: str
+    created_at: datetime
+    updated_at: datetime
+
+    class Config:
+        from_attributes = True
+
+# Full schema for viewing a single chat thread with all its messages.
+class ChatReadWithMessages(ChatReadSimple):
+    messages: list[MessageRead] = []

db/schemas/message.py

@@ -0,0 +1,29 @@
+import uuid
+from datetime import datetime
+from pydantic import BaseModel, Field, HttpUrl, computed_field
+from typing import Optional
+
+# -------------------
+# SCHEMAS FOR INPUT
+# -------------------
+class MessageCreate(BaseModel):
+    content: str = Field(..., description="The text content of the user's message.")
+
+# -------------------
+# SCHEMAS FOR OUTPUT
+# -------------------
+class MessageRead(BaseModel):
+    id: uuid.UUID
+    role: str
+    created_at: datetime
+
+    links: Optional[list[HttpUrl]] = None
+
+    @computed_field
+    @property
+    def content(self) -> str:
+        # self here is the SQLModel Message object
+        return self.answer
+
+    class Config:
+        from_attributes = True