Add InputStore and Enhance Template Renderer with Input Support

[httpdss]

Overview:
This PR introduces several changes, primarily aimed at improving input management during template generation and adding test coverage enhancements.

Changes:

• Added a new InputStore class to manage input data storage in JSON format.
• Updated the TemplateRenderer class to integrate with InputStore for loading and saving user inputs.
• Enhanced the generate.py module by adding the --input-store argument, enabling users to specify a file path for input storage.
• Refined argument handling in generate.py and improved the file creation process with the new input_store field.
• Minor changes to the FileItem class to support input_store integration.
• Added pytest-cov to the requirements.dev.txt for improved test coverage.

Justification:
These updates are part of an effort to streamline the input handling process for the structure generation tool. By using InputStore, the system can persistently manage user-provided inputs across sessions, reducing redundant data entry. Additionally, the integration with TemplateRenderer allows for smoother processing of template variables.

Impact:

• Enhanced user experience by minimizing repetitive input prompts.
• Improved maintainability and flexibility in handling structured data.
• Additional test coverage through the inclusion of pytest-cov.