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

lib/models/requests/send_message_request.dart

@@ -1,54 +0,0 @@
-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_request.freezed.dart";
-part "send_message_request.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);
-}