fix: correct email-in-address format, remove dead code, update tests (#110)

- Fix email format in AuthService.get_email_in_address to use
  receipts+{token}@receipts.cartsnitch.com (was broken: @email.cartsnitch.com)
- Remove dead EmailInAddressResponse class and GET /auth/me/email-in-address
  endpoint from auth/routes.py (endpoint moved to routes/user.py)
- Add instructions field to EmailInAddressResponse schema
- Update routes/user.py to include instructions in the response
- Update test URLs from /auth/me/email-in-address to /api/v1/me/email-in-address

Co-authored-by: CartSnitch Engineer Bot <cartnoreply@cartsnitch.com>
Co-authored-by: Paperclip <noreply@paperclip.ing>

src/cartsnitch_api/routes/user.py

@@ -19,7 +19,13 @@ async def get_email_in_address(
     svc = AuthService(db)
     try:
         email_address = await svc.get_email_in_address(user_id)
-        return EmailInAddressResponse(email_address=email_address)
+        return EmailInAddressResponse(
+            email_address=email_address,
+            instructions=(
+                "Forward your digital receipt emails to this address. "
+                "We currently support Meijer, Kroger, and Target receipt emails."
+            ),
+        )
     except LookupError:
         raise HTTPException(
             status_code=status.HTTP_404_NOT_FOUND, detail="User not found"