Add pipeline behaviors for signing process

Introduced four new pipeline behaviors (`AnnotationBehavior`,
`DocStatusBehavior`, `HistoryBehavior`, and `SendSignedMailBehavior`)
to modularize the signing process. These behaviors handle annotation
persistence, document status creation, history recording, and signed
mail notifications, respectively.

- `AnnotationBehavior`: Saves annotations using `IRepository`.
- `DocStatusBehavior`: Creates document status via `ISender`.
- `HistoryBehavior`: Records signing history and validates receiver
  information.
- `SendSignedMailBehavior`: Sends signed mail notifications using
  email templates and dynamic placeholder replacement.

Added error handling for missing data in `HistoryBehavior` and
`SendSignedMailBehavior`. Updated the signing pipeline to execute
these behaviors sequentially, ensuring a structured and extensible
workflow.

EnvelopeGenerator.Application/Signature/Behaviors/SendSignedMailBehavior.cs

@@ -0,0 +1,122 @@
+using DigitalData.Core.Abstraction.Application.Repository;
+using DigitalData.EmailProfilerDispatcher.Abstraction.Entities;
+using EnvelopeGenerator.Application.Common.Configurations;
+using EnvelopeGenerator.Application.Common.Extensions;
+using EnvelopeGenerator.Application.Signature.Commands;
+using EnvelopeGenerator.Domain.Constants;
+using EnvelopeGenerator.Domain.Entities;
+using EnvelopeGenerator.Domain.Interfaces;
+using MediatR;
+using Microsoft.EntityFrameworkCore;
+using Microsoft.Extensions.Options;
+using Newtonsoft.Json;
+
+namespace EnvelopeGenerator.Application.Signature.Behaviors;
+
+/// <summary>
+/// Pipeline behavior that sends signed mail notification.
+/// Executes LAST in the signing process - only if all previous behaviors succeed.
+/// </summary>
+public class SendSignedMailBehavior : IPipelineBehavior<SignCommand, Unit>
+{
+    private readonly IRepository<EmailTemplate> _tempRepo;
+    private readonly IRepository<EmailOut> _emailOutRepo;
+    private readonly MailParams _mailParams;
+    private readonly DispatcherParams _dispatcherParams;
+
+    /// <summary>
+    /// 
+    /// </summary>
+    /// <param name="tempRepo"></param>
+    /// <param name="emailOutRepo"></param>
+    /// <param name="mailParamsOptions"></param>
+    /// <param name="dispatcherParamsOptions"></param>
+    public SendSignedMailBehavior(
+        IRepository<EmailTemplate> tempRepo,
+        IRepository<EmailOut> emailOutRepo,
+        IOptions<MailParams> mailParamsOptions,
+        IOptions<DispatcherParams> dispatcherParamsOptions)
+    {
+        _tempRepo = tempRepo;
+        _emailOutRepo = emailOutRepo;
+        _mailParams = mailParamsOptions.Value;
+        _dispatcherParams = dispatcherParamsOptions.Value;
+    }
+
+    /// <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)
+    {
+        var placeHolders = CreatePlaceHolders(request);
+
+        var temp = await _tempRepo
+            .Where(x => x.Name == EmailTemplateType.DocumentSigned.ToString())
+            .SingleOrDefaultAsync(cancellationToken)
+                ?? throw new InvalidOperationException($"Email template not found. SignCommand:\n {request.ToJson(Format.Json.ForDiagnostics)}");
+
+        temp.Subject = ReplacePlaceHolders(temp.Subject, placeHolders, _mailParams.Placeholders);
+        temp.Body = ReplacePlaceHolders(temp.Body, placeHolders, _mailParams.Placeholders);
+
+        var emailOut = new EmailOut
+        {
+            EmailAddress = request.EmailAddress,
+            EmailBody = temp.Body,
+            EmailSubj = temp.Subject,
+            AddedWhen = DateTime.Now,
+            AddedWho = _dispatcherParams.AddedWho,
+            SendingProfile = _dispatcherParams.SendingProfile,
+            ReminderTypeId = _dispatcherParams.ReminderTypeId,
+            EmailAttmt1 = _dispatcherParams.EmailAttmt1,
+            WfId = (int)EnvelopeStatus.MessageConfirmationSent,
+            ReferenceString = request.EmailAddress,
+            ReferenceId = request.EnvelopeReceiver.ReceiverId
+        };
+
+        await _emailOutRepo.CreateAsync(emailOut, cancellationToken);
+
+        return await next();
+    }
+
+    private Dictionary<string, string> CreatePlaceHolders(SignCommand request)
+    {
+        var placeHolders = new Dictionary<string, string>()
+        {
+            { "[NAME_RECEIVER]", request.EnvelopeReceiver.Name ?? string.Empty },
+            { "[DOCUMENT_TITLE]", request.EnvelopeReceiver.Envelope?.Title ?? string.Empty },
+        };
+
+        if (request.EnvelopeReceiver.Envelope.IsReadAndConfirm())
+        {
+            placeHolders["[SIGNATURE_TYPE]"] = "Lesen und bestätigen";
+            placeHolders["[DOCUMENT_PROCESS]"] = string.Empty;
+            placeHolders["[FINAL_STATUS]"] = "Lesebestätigung";
+            placeHolders["[FINAL_ACTION]"] = "Empfänger bestätigt";
+            placeHolders["[REJECTED_BY_OTHERS]"] = "anderen Empfänger abgelehnt!";
+            placeHolders["[RECEIVER_ACTION]"] = "bestätigt";
+        }
+        else
+        {
+            placeHolders["[SIGNATURE_TYPE]"] = "Signieren";
+            placeHolders["[DOCUMENT_PROCESS]"] = " und elektronisch unterschreiben";
+            placeHolders["[FINAL_STATUS]"] = "Signatur";
+            placeHolders["[FINAL_ACTION]"] = "Vertragspartner unterzeichnet";
+            placeHolders["[REJECTED_BY_OTHERS]"] = "anderen Vertragspartner abgelehnt! Ihre notwendige Unterzeichnung wurde verworfen.";
+            placeHolders["[RECEIVER_ACTION]"] = "unterschrieben";
+        }
+
+        return placeHolders;
+    }
+
+    private static string ReplacePlaceHolders(string text, params Dictionary<string, string>[] placeHoldersList)
+    {
+        foreach (var placeHolders in placeHoldersList)
+            foreach (var ph in placeHolders)
+                text = text.Replace(ph.Key, ph.Value);
+        return text;
+    }
+}