Refactor project structure and add new features

Restructured project files across all layers:
- Removed `Controllers` folder reference from `DocumentOperator.API.csproj`.
- Added folder structure to `DocumentOperator.Application`, `DocumentOperator.Domain`, and `DocumentOperator.Infrastructure` projects for better organization.

Introduced new API configurations and middleware:
- Added `SerilogConfiguration` and `SwaggerConfiguration` classes.
- Added `ExceptionHandlingMiddleware`, `RequestLoggingMiddleware`, and `TenantResolutionMiddleware`.

Implemented new document processing feature:
- Added `ProcessDocumentCommand`, `ProcessDocumentHandler`, and `ProcessDocumentValidator` classes in the application layer.

DocumentOperator.API/Configuration/SerilogConfiguration.cs

@@ -0,0 +1,6 @@
+namespace DocumentOperator.API.Configuration
+{
+    public class SerilogConfiguration
+    {
+    }
+}

DocumentOperator.API/Configuration/SwaggerConfiguration.cs

@@ -0,0 +1,6 @@
+namespace DocumentOperator.API.Configuration
+{
+    public class SwaggerConfiguration
+    {
+    }
+}

DocumentOperator.API/DocumentOperator.API.csproj

@@ -19,8 +19,4 @@
     <ProjectReference Include="..\DocumentOperator.Infrastructure\DocumentOperator.Infrastructure.csproj" />
   </ItemGroup>
 
-  <ItemGroup>
-    <Folder Include="Controllers\" />
-  </ItemGroup>
-
 </Project>

DocumentOperator.API/Endpoints/v1/DocumentEndpoints.cs

@@ -0,0 +1,6 @@
+namespace DocumentOperator.API.Endpoints.v1
+{
+    public class DocumentEndpoints
+    {
+    }
+}

DocumentOperator.API/Middleware/ExceptionHandlingMiddleware.cs

@@ -0,0 +1,6 @@
+namespace DocumentOperator.API.Middleware
+{
+    public class ExceptionHandlingMiddleware
+    {
+    }
+}

DocumentOperator.API/Middleware/RequestLoggingMiddleware.cs

@@ -0,0 +1,6 @@
+namespace DocumentOperator.API.Middleware
+{
+    public class RequestLoggingMiddleware
+    {
+    }
+}

DocumentOperator.API/Middleware/TenantResolutionMiddleware.cs

@@ -0,0 +1,6 @@
+namespace DocumentOperator.API.Middleware
+{
+    public class TenantResolutionMiddleware
+    {
+    }
+}