Initial commit.

- Created and set up main projects
- Created classes for Domain

PhonebookService.Domain/Queries/SortMode.cs

@@ -0,0 +1,11 @@
+namespace PhonebookService.Domain.Queries;
+
+/// <summary>
+/// Sorting options for <see cref="PhonebookFilterQuery"/>
+/// </summary>
+public enum SortMode
+{
+	Ascending = 1,
+	None = 0,
+	Descending = -1
+}