Fix issue with file handling in generate_file function

[sunnysktsang]

Problem:
The generate_file function in the utils.py module had a bug where the file streams were not managed properly, causing an "I/O operation on closed file" error when attempting to upload files. This error obstructed the functionality of uploading and processing files through the application.

Changes Made:

• Implemented the use of context managers (with statement) to ensure that file streams are properly opened and closed, preventing any premature closure that could lead to the mentioned error.
• Adjusted the handling of file streams to keep the file open during the operation and ensure it is only closed after the operation completes.
• Added additional error handling to manage scenarios where files might not be accessible or present.

Benefits:

• Ensures that the file handling process is robust and error-free.
• Prevents common file handling errors that could disrupt user operations, enhancing the reliability of the file upload feature.
• Improves the stability of the application by ensuring resources are managed and released properly.

Tests Conducted:

• Manually tested with various file sizes and formats to ensure that files are handled correctly without causing any errors.
• Verified that the changes did not negatively impact other functionalities of the application.

Additional Notes:

• These changes are crucial for the operations where file interaction is frequent and critical to the application's functionality.
• Future recommendations include implementing automated tests to cover file handling scenarios.