Refactor Email to EmailContext across codebase

Replaced the `Email` record with the new `EmailContext` record to introduce additional context and functionality in email handling. Updated property definitions to distinguish between .NET Framework (`set`) and other frameworks (`init`).

Modified `SendingEmailEvent` to use `EmailContext` for the `Mail` property. Updated mappings in `EmailMappingProfile` to map `SendEmailCommand` to `EmailContext`. Adjusted `SendEmailCommandHandler` to use `EmailContext` when mapping requests.

Refactored `EmailSender` to use `EmailContext` in its `Send` method, including updates to method signatures and documentation. Updated all related test classes (`EmailSenderTests`, `EmailSenderUrlOverloadTests`, `SendingEmailPublisherTests`) to validate the behavior of `EmailContext`, ensuring consistency and thorough testing of the transition.

These changes ensure compatibility across frameworks and improve the maintainability of the email handling process.

src/core/DigitalData.MessagingService.Abstraction/EmailContext.cs

@@ -0,0 +1,48 @@
+namespace DigitalData.MessagingService.Abstraction;
+
+public record EmailContext
+{
+#if NETFRAMEWORK
+    public EmailAccountDto Sender { get; set; } = null!;
+#else
+    public required EmailAccountDto Sender { get; init; }
+#endif
+
+    /// <summary>
+    /// Recipient email address
+    /// </summary>
+
+#if NETFRAMEWORK
+    public IEnumerable<string> Recipients { get; set; } = null!;
+#else
+    public required IEnumerable<string> Recipients { get; init; }
+#endif
+
+    /// <summary>
+    /// Email subject
+    /// </summary>
+
+#if NETFRAMEWORK
+    public string Subject { get; set; } = null!;
+#else
+    public required string Subject { get; init; }
+#endif
+
+    /// <summary>
+    /// Email body (HTML or plain text)
+    /// </summary>
+#if NETFRAMEWORK
+    public string Body { get; set; } = null!;
+#else
+    public required string Body { get; init; }
+#endif
+
+    /// <summary>
+    /// Is HTML email (default: true)
+    /// </summary>
+#if NETFRAMEWORK
+    public bool IsHtml { get; set; } = true;
+#else
+    public bool IsHtml { get; init; } = true;
+#endif
+}