Refactor namespaces for SignCommand and behaviors

Updated namespaces from `Signature` to `Signatures` for consistency and clarity across the application. Simplified pipeline behavior registrations in `DependencyInjection.cs` by using shorter references. Added `Microsoft.Extensions.Configuration` to `DependencyInjection.cs` to support configuration functionality. Ensured all references to `SignCommand` and related behaviors align with the new namespace structure.

EnvelopeGenerator.Application/Signatures/Behaviors/AnnotationBehavior.cs

@@ -0,0 +1,41 @@
+using DigitalData.Core.Abstraction.Application.Repository;
+using EnvelopeGenerator.Application.Common.Dto;
+using EnvelopeGenerator.Application.Signatures.Commands;
+using EnvelopeGenerator.Domain.Entities;
+using MediatR;
+
+namespace EnvelopeGenerator.Application.Signatures.Behaviors;
+
+/// <summary>
+/// Pipeline behavior that saves annotations.
+/// Executes first in the signing process.
+/// </summary>
+[Obsolete("This notification is deprecated. Use Signature.Commands.SignCommand instead.")]
+public class AnnotationBehavior : IPipelineBehavior<SignCommand, Unit>
+{
+    private readonly IRepository<ElementAnnotation> _repo;
+
+    /// <summary>
+    /// 
+    /// </summary>
+    /// <param name="repository"></param>
+    public AnnotationBehavior(IRepository<ElementAnnotation> repository)
+    {
+        _repo = repository;
+    }
+
+    /// <summary>
+    /// 
+    /// </summary>
+    /// <param name="request"></param>
+    /// <param name="next"></param>
+    /// <param name="cancellationToken"></param>
+    /// <returns></returns>
+    public async Task<Unit> Handle(SignCommand request, RequestHandlerDelegate<Unit> next, CancellationToken cancellationToken)
+    {
+        if (request.PsPdfKitAnnotation is PsPdfKitAnnotation annot)
+            await _repo.CreateAsync(annot.Structured, cancellationToken);
+
+        return await next();
+    }
+}