Add filtering logic for receiver suggestions

Introduce `ReceiverFilterCriteria` to encapsulate filtering criteria for receivers, including normalization of `FullName` and `EmailAddress`. Add `ReceiverSuggestionFilterHandler` to filter `RecentReceiverSuggestionDto` objects based on the criteria. Includes methods for matching criteria and filtering suggestions.

EnvelopeGenerator.Server/EnvelopeGenerator.Server.Client/Components/Sender/ReceiverSuggestionFilter/ReceiverFilterCriteria.cs

@@ -0,0 +1,25 @@
+namespace EnvelopeGenerator.Server.Client.Components.Sender.ReceiverSuggestionFilter;
+
+public readonly record struct ReceiverFilterCriteria
+{
+    public readonly string FullName;
+    public readonly string EmailAddress;
+
+    public ReceiverFilterCriteria(string? fullName = "", string? emailAddress = "")
+    {
+        FullName = Normalize(fullName);
+        EmailAddress = Normalize(emailAddress);
+    }
+
+    public readonly bool Matches(ReceiverFilterCriteria criteria)
+        => FullName.Contains(criteria.FullName, StringComparison.Ordinal)
+           && EmailAddress.Contains(criteria.EmailAddress, StringComparison.Ordinal);
+
+    private static string Normalize(string? text)
+    {
+        if (string.IsNullOrWhiteSpace(text))
+            return string.Empty;
+
+        return string.Concat(text.Where(c => !char.IsWhiteSpace(c))).ToLowerInvariant();
+    }
+}

EnvelopeGenerator.Server/EnvelopeGenerator.Server.Client/Components/Sender/ReceiverSuggestionFilter/ReceiverSuggestionFilterHandler.cs

@@ -0,0 +1,26 @@
+using EnvelopeGenerator.Application.Common.Dto.Receiver;
+
+namespace EnvelopeGenerator.Server.Client.Components.Sender.ReceiverSuggestionFilter;
+
+public class ReceiverSuggestionFilterHandler(IEnumerable<RecentReceiverSuggestionDto> suggestions)
+{
+    private readonly IReadOnlyList<Entry> _entries = suggestions
+        .Where(x => !string.IsNullOrWhiteSpace(x.FullName) && !string.IsNullOrWhiteSpace(x.EmailAddress))
+        .Select(x => new Entry(new ReceiverFilterCriteria(x.FullName, x.EmailAddress), x))
+        .ToList();
+
+    private readonly record struct Entry(ReceiverFilterCriteria Criteria, RecentReceiverSuggestionDto Suggestion);
+
+    public IEnumerable<RecentReceiverSuggestionDto> Filter(ReceiverFilterCriteria criteria)
+    {
+        return _entries
+            .Where(x => x.Criteria.Matches(criteria))
+            .Select(x => x.Suggestion);
+    }
+
+    public IEnumerable<RecentReceiverSuggestionDto> Filter(string fullName, string emailAddress)
+    {
+        var criteria = new ReceiverFilterCriteria(fullName, emailAddress);
+        return Filter(criteria);
+    }
+}