Refactor: Ensure correct type for PostgresDsn instantiation

[heysaeid]

Summary

This PR resolves a PydanticSerializationUnexpectedValue warning that occurs when building the PostgreSQL connection DSN.

The Problem

The code was assigning a raw formatted string to a field that is typed as pydantic.networks.PostgresDsn. This caused Pydantic to raise the following warning during serialization:

pydantic/main.py:463: UserWarning: Pydantic serializer warnings:
PydanticSerializationUnexpectedValue(Expected <class 'pydantic.networks.PostgresDsn'> but got <class 'str'> with value '...' - serialized value may not be as expected.)

The Solution

The fix is to explicitly instantiate the PostgresDsn class with the connection string. This ensures that the field holds an object of the correct type, leverages Pydantic's validation, and silences the warning.