treewide(refactor): rename files to follow the same style

lib/models/requests/send_message.dart

@@ -0,0 +1,54 @@
+import "package:fast_immutable_collections/fast_immutable_collections.dart";
+import "package:freezed_annotation/freezed_annotation.dart";
+import "package:nexus/models/relation_type.dart";
+part "send_message.freezed.dart";
+part "send_message.g.dart";
+
+@freezed
+abstract class SendMessageRequest with _$SendMessageRequest {
+  const factory SendMessageRequest({
+    required String roomId,
+    required String text,
+    @Default(Mentions()) @JsonKey(name: "mentions") Mentions mentions,
+    @JsonKey(name: "relates_to") Relation? relation,
+  }) = _SendMessageRequest;
+
+  factory SendMessageRequest.fromJson(Map<String, Object?> json) =>
+      _$SendMessageRequestFromJson(json);
+}
+
+@freezed
+abstract class Mentions with _$Mentions {
+  const factory Mentions({
+    @Default(false) bool room,
+    @Default(IList.empty()) IList<String> userIds,
+  }) = _Mentions;
+
+  factory Mentions.fromJson(Map<String, Object?> json) =>
+      _$MentionsFromJson(json);
+}
+
+@Freezed(toJson: false)
+abstract class Relation with _$Relation {
+  const Relation._();
+
+  const factory Relation({
+    required String eventId,
+    required RelationType relationType,
+  }) = _Relation;
+
+  Map<String, dynamic> toJson() {
+    switch (relationType) {
+      case RelationType.reply:
+        return {
+          "m.in_reply_to": {"event_id": eventId},
+        };
+
+      case RelationType.edit:
+        return {"rel_type": "m.replace", "event_id": eventId};
+    }
+  }
+
+  factory Relation.fromJson(Map<String, dynamic> json) =>
+      _$RelationFromJson(json);
+}