SomniaGuestLog - Address search/query using Nominatim - Initial implementation

Initial implementation for address search/query using external APIs (OSM Nominatim) & Added required classes for supporting more APIs in the future.

src/Somnia.GuestLog/Services/AddressQuery/IAddressQueryService.cs

@@ -0,0 +1,19 @@
+using Somnia.GuestLog.Models.DTOs;
+
+namespace Somnia.GuestLog.Services.AddressQuery;
+
+public interface IAddressQueryService
+{
+
+    /// <summary>
+    /// Search an address by plain text query.
+    /// Data is returned as a structured address.
+    /// This service allow to complete and validate addresses.
+    /// 
+    /// Note: Not all fields are always available for a given query.
+    /// </summary>
+    /// <param name="query">Address to search</param>
+    /// <returns>List of resulting structured addresses</returns>
+    public Task<List<AddressResultDTO>> SearchAddressAsync(string query);
+
+}