refactor: re-write gen_gql_schema.rs #1510

[snigdha510]

Summary:
In this PR, the gen_gql_schema.rs file has been updated to address code quality and performance issues, specifically:

Enhanced Functionality:

Introduced new functions for better modularity and readability, including write_all_directives, write_all_input_types, write_property, write_directive, and others. These functions streamline the code and reduce redundancy.
Documentation:

Added comments and documentation to clarify the purpose and functionality of various functions and structures, improving code maintainability.
Improved Indentation Handling:

Implemented IndentedWriter to manage indentation consistently across the generated GraphQL schema, ensuring more readable output.
Optimized Type Handling:

Improved handling of schema types, including arrays and objects, by modularizing type writing logic into functions like write_type, write_array_validation, and write_object_validation.
Directive and Object Handling:

Refined logic for writing directives and objects, including better handling of entity mappings and directive properties, enhancing flexibility and robustness.
Enhanced Scalability:

Improved the handling of custom scalars and extended types, allowing for more scalable and extensible schema generation.
Code Cleanup:

Removed redundant code, fixed minor bugs, and applied general code cleanups to improve performance and readability.
These changes collectively improve the maintainability, readability, and extensibility of the GraphQL schema generation process.

Issue Reference(s):
Fixes #.1510

Build & Testing:

• I ran cargo test successfully.
• I have run ./lint.sh --mode=fix to fix all linting issues raised by ./lint.sh --mode=check.

Checklist:

• I have added relevant unit & integration tests.
• I have updated the documentation accordingly.
• I have performed a self-review of my code.
• PR follows the naming convention of <type>(<optional scope>): <title>

[tusharmath]

You will also need to write code to generate the service documents for each Config entity. Moving to draft until then.

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