Introduced a new `DocumentService.Client` project targeting `net462`, `net480`, and `net8.0`. The project includes metadata for NuGet packaging, such as `PackageId`, `Authors`, and `Company`, and references `Microsoft.Extensions.DependencyInjection` and `Microsoft.Extensions.Logging`.
Updated `DocumentService.sln` to include the new project, its build configurations, and solution folder associations.
Added `icon.png` as the NuGet package icon and included it in the project file.
This commit implements a complete rebranding of the project:
- Updated all namespaces from `DocumentOperator` to `DocumentService`.
- Renamed file paths, embedded resources, and test data references.
- Updated configuration keys, logging paths, and Redis instance names.
- Revised documentation to reflect the new project name.
- Modified project and solution files to align with the new structure.
- Updated class names, DTOs, commands, queries, and handlers.
- Adjusted middleware, controllers, and API endpoints.
- Updated Swagger metadata and API titles to `DocumentService API`.
- Refactored test namespaces, resource paths, and embedded resources.
- Updated build and deployment configurations for the new name.
- Replaced all references to `DocumentOperator` in comments and literals.
These changes ensure consistency across the codebase and documentation.
