Agents - Introduce agent system app to v25.x (#2458)

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#### Summary 
Introducing Agent System app

#### Work Item(s) 
Fixes
[AB#559557](https://dynamicssmb2.visualstudio.com/1fcb79e7-ab07-432a-a3c6-6cf5a88ba4a5/_workitems/edit/559557)

src/System Application/App/Agent/Interaction/AgentMessage.Codeunit.al

@@ -0,0 +1,75 @@
+// ------------------------------------------------------------------------------------------------
+// Copyright (c) Microsoft Corporation. All rights reserved.
+// Licensed under the MIT License. See License.txt in the project root for license information.
+// ------------------------------------------------------------------------------------------------
+
+namespace System.Agents;
+
+codeunit 4307 "Agent Message"
+{
+    InherentEntitlements = X;
+    InherentPermissions = X;
+
+    /// <summary>
+    /// Get the message text for the given agent task message.
+    /// </summary>
+    /// <param name="AgentTaskMessage">Agent task message.</param>
+    /// <returns>The body of the agent task message.</returns>
+    [Scope('OnPrem')]
+    procedure GetText(var AgentTaskMessage: Record "Agent Task Message"): Text
+    var
+        AgentMessageImpl: Codeunit "Agent Message Impl.";
+    begin
+        exit(AgentMessageImpl.GetMessageText(AgentTaskMessage));
+    end;
+
+    /// <summary>
+    /// Updates the message text.
+    /// </summary>
+    /// <param name="AgentTaskMessage">The message record to update.</param>
+    /// <param name="NewMessageText">New message text to set.</param>
+    [Scope('OnPrem')]
+    procedure UpdateText(var AgentTaskMessage: Record "Agent Task Message"; NewMessageText: Text)
+    var
+        AgentMessageImpl: Codeunit "Agent Message Impl.";
+    begin
+        AgentMessageImpl.UpdateText(AgentTaskMessage, NewMessageText);
+    end;
+
+    /// <summary>
+    /// Check if it is possible to edit the message.
+    /// </summary>
+    /// <param name="AgentTaskMessage">Agent task message to verify.</param>
+    /// <returns>If it is possible to change the message.</returns>
+    [Scope('OnPrem')]
+    procedure IsEditable(var AgentTaskMessage: Record "Agent Task Message"): Boolean
+    var
+        AgentMessageImpl: Codeunit "Agent Message Impl.";
+    begin
+        exit(AgentMessageImpl.IsMessageEditable(AgentTaskMessage));
+    end;
+
+    /// <summary>
+    /// Sets the message status to sent.
+    /// </summary>
+    /// <param name="AgentTaskMessage">Agent task message to update status.</param>
+    [Scope('OnPrem')]
+    procedure SetStatusToSent(var AgentTaskMessage: Record "Agent Task Message")
+    var
+        AgentMessageImpl: Codeunit "Agent Message Impl.";
+    begin
+        AgentMessageImpl.SetStatusToSent(AgentTaskMessage);
+    end;
+
+    /// <summary>
+    /// Downloads the attachments for a specific message.
+    /// </summary>
+    /// <param name="AgentTaskMessage">Message to download attachments for.</param>
+    [Scope('OnPrem')]
+    procedure DownloadAttachments(var AgentTaskMessage: Record "Agent Task Message")
+    var
+        AgentMessageImpl: Codeunit "Agent Message Impl.";
+    begin
+        AgentMessageImpl.DownloadAttachments(AgentTaskMessage);
+    end;
+}

src/System Application/App/Agent/Interaction/AgentMessageImpl.Codeunit.al

@@ -0,0 +1,80 @@
+// ------------------------------------------------------------------------------------------------
+// Copyright (c) Microsoft Corporation. All rights reserved.
+// Licensed under the MIT License. See License.txt in the project root for license information.
+// ------------------------------------------------------------------------------------------------
+
+namespace System.Agents;
+
+codeunit 4308 "Agent Message Impl."
+{
+    Access = Internal;
+    InherentEntitlements = X;
+    InherentPermissions = X;
+
+    procedure GetMessageText(var AgentTaskMessage: Record "Agent Task Message"): Text
+    var
+        AgentTaskImpl: Codeunit "Agent Task Impl.";
+        ContentInStream: InStream;
+        ContentText: Text;
+    begin
+        AgentTaskMessage.CalcFields(Content);
+        AgentTaskMessage.Content.CreateInStream(ContentInStream, AgentTaskImpl.GetDefaultEncoding());
+        ContentInStream.Read(ContentText);
+        exit(ContentText);
+    end;
+
+    procedure UpdateText(var AgentTaskMessage: Record "Agent Task Message"; NewMessageText: Text)
+    var
+        AgentTaskImpl: Codeunit "Agent Task Impl.";
+        ContentOutStream: OutStream;
+    begin
+        Clear(AgentTaskMessage.Content);
+        AgentTaskMessage.Content.CreateOutStream(ContentOutStream, AgentTaskImpl.GetDefaultEncoding());
+        ContentOutStream.Write(NewMessageText);
+        AgentTaskMessage.Modify(true);
+    end;
+
+    procedure IsMessageEditable(var AgentTaskMessage: Record "Agent Task Message"): Boolean
+    begin
+        if AgentTaskMessage.Type <> AgentTaskMessage.Type::Output then
+            exit(false);
+
+        exit(AgentTaskMessage.Status = AgentTaskMessage.Status::Draft);
+    end;
+
+    procedure SetStatusToSent(var AgentTaskMessage: Record "Agent Task Message")
+    begin
+        UpdateAgentTaskMessageStatus(AgentTaskMessage, AgentTaskMessage.Status::Sent);
+    end;
+
+    procedure DownloadAttachments(var AgentTaskMessage: Record "Agent Task Message")
+    var
+        AgentTaskFile: Record "Agent Task File";
+        AgentTaskMessageAttachment: Record "Agent Task Message Attachment";
+        AgentTaskImpl: Codeunit "Agent Task Impl.";
+        InStream: InStream;
+        FileName: Text;
+        DownloadDialogTitleLbl: Label 'Download Email Attachment';
+    begin
+        AgentTaskMessageAttachment.SetRange("Task ID", AgentTaskMessage."Task ID");
+        AgentTaskMessageAttachment.SetRange("Message ID", AgentTaskMessage.ID);
+        if not AgentTaskMessageAttachment.FindSet() then
+            exit;
+
+        repeat
+            if not AgentTaskFile.Get(AgentTaskMessageAttachment."Task ID", AgentTaskMessageAttachment."File ID") then
+                exit;
+
+            FileName := AgentTaskFile."File Name";
+            AgentTaskFile.CalcFields(Content);
+            AgentTaskFile.Content.CreateInStream(InStream, AgentTaskImpl.GetDefaultEncoding());
+            File.DownloadFromStream(InStream, DownloadDialogTitleLbl, '', '', FileName);
+        until AgentTaskMessageAttachment.Next() = 0;
+    end;
+
+    procedure UpdateAgentTaskMessageStatus(var AgentTaskMessage: Record "Agent Task Message"; Status: Option)
+    begin
+        AgentTaskMessage.Status := Status;
+        AgentTaskMessage.Modify(true);
+    end;
+}

src/System Application/App/Agent/Interaction/AgentTask.Codeunit.al

@@ -0,0 +1,41 @@
+// ------------------------------------------------------------------------------------------------
+// Copyright (c) Microsoft Corporation. All rights reserved.
+// Licensed under the MIT License. See License.txt in the project root for license information.
+// ------------------------------------------------------------------------------------------------
+
+namespace System.Agents;
+
+codeunit 4303 "Agent Task"
+{
+    InherentEntitlements = X;
+    InherentPermissions = X;
+
+    /// <summary>
+    /// Check if a task exists for the given agent user and conversation
+    /// </summary>
+    /// <param name="AgentUserSecurityID">The user security ID of the agent.</param>
+    /// <param name="ConversationId">The conversation ID to check.</param>
+    /// <returns>True if task exists, false if not.</returns>
+    [Scope('OnPrem')]
+    procedure TaskExists(AgentUserSecurityId: Guid; ConversationId: Text): Boolean
+    var
+        AgentTaskImpl: Codeunit "Agent Task Impl.";
+    begin
+        exit(AgentTaskImpl.TaskExists(AgentUserSecurityId, ConversationId));
+    end;
+
+    /// <summary>
+    /// Create a new task message for the given agent user and conversation.
+    /// If task does not exist, it will be created.
+    /// </summary>
+    /// <param name="From">Specifies from address.</param>
+    /// <param name="MessageText">The message text for the task.</param>
+    /// <param name="CurrentAgentTask">Current Agent Task to which the message will be added.</param>
+    [Scope('OnPrem')]
+    procedure CreateTaskMessage(From: Text[250]; MessageText: Text; ExternalMessageId: Text[2048]; var CurrentAgentTask: Record "Agent Task")
+    var
+        AgentTaskImpl: Codeunit "Agent Task Impl.";
+    begin
+        AgentTaskImpl.CreateTaskMessage(From, MessageText, ExternalMessageId, CurrentAgentTask);
+    end;
+}