add support for sending media

Still needs camera support.

lib/models/requests/send_message.dart

@@ -1,5 +1,6 @@
 import "package:fast_immutable_collections/fast_immutable_collections.dart";
 import "package:freezed_annotation/freezed_annotation.dart";
+import "package:nexus/models/content/content.dart";
 import "package:nexus/models/relation_type.dart";
 part "send_message.freezed.dart";
 part "send_message.g.dart";
@@ -9,6 +10,7 @@ abstract class SendMessageRequest with _$SendMessageRequest {
   const factory SendMessageRequest({
     required String roomId,
     required String text,
+    Content? baseContent,
     @Default(Mentions()) @JsonKey(name: "mentions") Mentions mentions,
     @JsonKey(name: "relates_to") Relation? relation,
   }) = _SendMessageRequest;

lib/models/requests/upload_media.dart

@@ -0,0 +1,24 @@
+import "package:freezed_annotation/freezed_annotation.dart";
+part "upload_media.freezed.dart";
+part "upload_media.g.dart";
+
+@freezed
+abstract class UploadMediaRequest with _$UploadMediaRequest {
+  const factory UploadMediaRequest({
+    required String path,
+    required bool encrypted,
+    String? filename,
+    @Default(false) @JsonKey(name: "voice_message") bool isVoiceMessage,
+    @Default(false) bool forceFile,
+
+    // Below params only work if encodeTo is set
+    String? encodeTo,
+    int? resizeWidth,
+    int? resizeHeight,
+    int? resizePercent,
+    @Default(80) int quality,
+  }) = _UploadMediaRequest;
+
+  factory UploadMediaRequest.fromJson(Map<String, Object?> json) =>
+      _$UploadMediaRequestFromJson(json);
+}