added a swipeable media gallery for chat and folder images and videos with server previews, on-demand originals and zoom, and marked document previews in chat so they no longer pass for photos

lib/api/marianumcloud/talk/chat/get_chat_response.dart

@@ -165,7 +165,17 @@ class RichObjectString {
   String? path;
   String? link;
 
-  RichObjectString(this.type, this.id, this.name, this.path, this.link);
+  /// Only set for `file` objects.
+  String? mimetype;
+
+  RichObjectString(
+    this.type,
+    this.id,
+    this.name,
+    this.path,
+    this.link, [
+    this.mimetype,
+  ]);
 
   factory RichObjectString.fromJson(Map<String, dynamic> json) =>
       _$RichObjectStringFromJson(json);

lib/api/marianumcloud/talk/chat/get_chat_response.g.dart

@@ -135,6 +135,7 @@ RichObjectString _$RichObjectStringFromJson(Map<String, dynamic> json) =>
         $checkedConvert('name', (v) => v as String),
         $checkedConvert('path', (v) => v as String?),
         $checkedConvert('link', (v) => v as String?),
+        $checkedConvert('mimetype', (v) => v as String?),
       );
       return val;
     });
@@ -146,6 +147,7 @@ Map<String, dynamic> _$RichObjectStringToJson(RichObjectString instance) =>
       'name': instance.name,
       'path': instance.path,
       'link': instance.link,
+      'mimetype': instance.mimetype,
     };
 
 const _$RichObjectStringObjectTypeEnumMap = {