Updated ROADMAP.md to mark Phase 2 as completed and added detailed descriptions of completed tasks. Introduced three new value objects (`Base64String`, `TenantId`, and `PdfMetadata`) in the `DocumentOperator.Domain.Models.ValueObjects` namespace. These classes ensure type safety, immutability, and encapsulated validation.
- `Base64String`: Handles Base64 string creation, validation, and conversion.
- `TenantId`: Represents a tenant identifier with validation and normalization.
- `PdfMetadata`: Represents PDF metadata with computed properties.
Updated `DocumentOperator.Domain.csproj` to reflect the addition of these value objects. The project is now ready to begin Phase 3 (Infrastructure Layer).
Updated ROADMAP.md to mark Step 2.2 ("Enums erstellen") as completed, documenting the creation of `DocumentOperationType` and `ProcessingStatus` enums.
Added `DocumentOperationType` and `ProcessingStatus` enums under the `DocumentOperator.Domain.Models.Enums` namespace to represent document operations and processing statuses, respectively.
Modified `DocumentOperator.Domain.csproj` to remove the `Models\Enums\` folder from the `<ItemGroup>` section, reflecting changes in the inclusion strategy for enums.
