feat: Add unit tests for run_flow_from_json with fake environment variables

[edwinjosechittilappilly]

Added Tests for run_flow_from_json Functionality

Description

This PR introduces new unit tests for the run_flow_from_json function to ensure it correctly handles environment variables. The following tests have been added:

• test_run_flow_with_fake_env: Validates the flow execution using a fake .env file, ensuring that the expected output is returned.
• test_run_flow_with_fake_env_TWEAKS: Checks the flow execution when environment variables are loaded from the fake .env file, confirming that the output matches the expected result.

Motivation

These tests enhance the reliability of the run_flow_from_json function by verifying its behavior with different configurations of environment variables, which is crucial for maintaining functionality in various deployment scenarios.

Changes

• Added test_run_flow_with_fake_env to test flow execution with a fake environment.
• Added test_run_flow_with_fake_env_TWEAKS to test flow execution with environment variables loaded from a fake .env file.
• Implemented a function to recursively replace keys in the tweaks dictionary with values from the provided environment variables. This Fixes the issue of ENV variables not loading when using run_flow_from_json