fixup! feat!: simplify usage of clientFactories

lib/src/core/servient.dart

@@ -40,15 +40,18 @@ class Servient {
   /// A custom [contentSerdes] can be passed that supports other media types
   /// than the default ones.
   Servient({
-    required List<ProtocolClientFactory> clientFactories,
+    List<ProtocolClientFactory>? clientFactories,
     ServerSecurityCallback? serverSecurityCallback,
     ContentSerdes? contentSerdes,
-  })  : _clientFactories = _processProtocolClientFactories(clientFactories),
-        contentSerdes = contentSerdes ?? ContentSerdes(),
-        _serverSecurityCallback = serverSecurityCallback;
+  })  : contentSerdes = contentSerdes ?? ContentSerdes(),
+        _serverSecurityCallback = serverSecurityCallback {
+    for (final clientFactory in clientFactories ?? <ProtocolClientFactory>[]) {
+      addClientFactory(clientFactory);
+    }
+  }
 
   final List<ProtocolServer> _servers = [];
-  final Map<String, ProtocolClientFactory> _clientFactories;
+  final Map<String, ProtocolClientFactory> _clientFactories = {};
   final Map<String, ExposedThing> _things = {};
   final Map<String, ConsumedThing> _consumedThings = {};
 
@@ -57,18 +60,6 @@ class Servient {
   /// The [ContentSerdes] object that is used for serializing/deserializing.
   final ContentSerdes contentSerdes;
 
-  static Map<String, ProtocolClientFactory> _processProtocolClientFactories(
-    List<ProtocolClientFactory> protocolFactories,
-  ) {
-    return Map.fromEntries(
-      protocolFactories.expand((protocolFactory) sync* {
-        for (final scheme in protocolFactory.schemes) {
-          yield MapEntry(scheme, protocolFactory);
-        }
-      }),
-    );
-  }
-
   /// Starts this [Servient] and returns a [WoT] runtime object.
   ///
   /// The [WoT] runtime can be used for consuming, procuding, and discovering
@@ -198,6 +189,21 @@ class Servient {
   List<String> get clientSchemes =>
       _clientFactories.keys.toList(growable: false);
 
+  /// Adds a new [clientFactory] to this [Servient].
+  void addClientFactory(ProtocolClientFactory clientFactory) {
+    for (final scheme in clientFactory.schemes) {
+      _clientFactories[scheme] = clientFactory;
+    }
+  }
+
+  /// Removes a [ProtocolClientFactory] matching the given [scheme] from this
+  /// [Servient], if present.
+  ///
+  /// If a [ProtocolClientFactory] was removed, the method returns it, otherwise
+  /// the return value is `null`.
+  ProtocolClientFactory? removeClientFactory(String scheme) =>
+      _clientFactories.remove(scheme);
+
   /// Checks whether a [ProtocolClient] is avaiable for a given [scheme].
   bool hasClientFor(String scheme) => _clientFactories.containsKey(scheme);