Enhance EnvelopeReceiver queries and controller

- Updated `EnvelopeReceiverQuery` to include an optional, nullable `Status` parameter.
- Modified `ReadEnvelopeReceiverQuery` to inherit from the updated `EnvelopeReceiverQuery`.
- Added new using directives in `EnvelopeReceiverController` and enhanced response documentation to include a 401 Unauthorized response.
- Implemented authorization for the `GetEnvelopeReceiver` method.
- Improved documentation and method signature for `GetReceiverName` to accept a `ReadReceiverNameQuery` object.
- Introduced a new `ReadReceiverNameQuery` record for querying the last used salutation of a receiver.

EnvelopeGenerator.Application/Envelopes/Queries/ReceiverName/ReadReceiverNameQuery.cs

@@ -0,0 +1,13 @@
+using EnvelopeGenerator.Application.Receivers.Queries.Read;
+
+namespace EnvelopeGenerator.Application.Envelopes.Queries.ReceiverName;
+
+/// <summary>
+/// Eine Abfrage, um die zuletzt verwendete Anrede eines Empfängers zu ermitteln, 
+/// damit diese für zukünftige Umschläge wiederverwendet werden kann.
+/// </summary>
+/// <param name="Envelope">Der Umschlag, für den die Anrede des Empfängers ermittelt werden soll.</param>
+/// <param name="OnlyLast">Gibt an, ob nur die zuletzt verwendete Anrede zurückgegeben werden soll.</param>
+public record ReadReceiverNameQuery(EnvelopeQuery? Envelope = null, bool OnlyLast = true) : ReadReceiverQuery
+{
+}