feat: Implement Companies Resource with Certificate Management

- Added Certificate Management specification including upload, validation, status retrieval, and replacement of digital certificates.
- Introduced Company CRUD Operations specification with create, list, retrieve, update, and delete functionalities.
- Developed tasks for implementing the Companies Resource, organized into phases for core enhancements, certificate management, search helpers, and documentation.
- Completed unit and integration tests for all new functionalities, ensuring high coverage and reliability.
- Updated documentation to reflect new capabilities and usage examples.

Author: andrekutianski