Add (WIP) ban/klck ability

lib/models/requests/set_membership_request.dart

@@ -0,0 +1,20 @@
+import "package:freezed_annotation/freezed_annotation.dart";
+part "set_membership_request.freezed.dart";
+part "set_membership_request.g.dart";
+
+@freezed
+abstract class SetMembershipRequest with _$SetMembershipRequest {
+  const factory SetMembershipRequest({
+    required String userId,
+    required String roomId,
+
+    @JsonKey(name: "action") required MembershipAction action,
+    @Default(false) @JsonKey(name: "msc4293_redact_events") bool redact,
+  }) = _SetMembershipRequest;
+
+  factory SetMembershipRequest.fromJson(Map<String, Object?> json) =>
+      _$SetMembershipRequestFromJson(json);
+}
+
+@JsonEnum()
+enum MembershipAction { ban, kick, unban, invite }