Refactor: Updated document creation logic and file structure

[HlexNC]

I have refactored the document creation logic and file structure to improve code organization and maintainability. This includes removing deprecated logic files and renaming the unit test file. Additionally, I have updated the document-generation-lib structure to use the documentManager module instead of the documentLibrary module. This change ensures that the document creation endpoints use the correct module for creating documents and buffers. The changes have been thoroughly tested and are ready for review.

@HlexNC ➜ /workspaces/UNIC-Document-Conversion-API/document-generation-lib (refactor/document-generation-restructure) $ npm test

> @universityofnicosia/[email protected] test
> jest

  console.log
    /workspaces/UNIC-Document-Conversion-API/document-generation-lib/tests_output/testDocument.docx has been created.

      at WriteStream.log (src/utils/officegenHelper.js:96:15)

  console.log
    /workspaces/UNIC-Document-Conversion-API/document-generation-lib/tests_output/testDocumentWithTable.docx has been created.

      at WriteStream.log (src/utils/officegenHelper.js:96:15)

 PASS  tests/document.test.js
  Document Gen API Tests
    ✓ should create a document with titles, text, and code blocks (82 ms)
    ✓ should generate a buffer for a document with paragraph content (33 ms)
    ✓ should create a document with a table (50 ms)

Test Suites: 1 passed, 1 total
Tests:       3 passed, 3 total
Snapshots:   0 total
Time:        0.573 s, estimated 1 s
Ran all test suites.
@HlexNC ➜ /workspaces/UNIC-Document-Conversion-API/document-generation-lib (refactor/document-generation-restructure) $