Add field “unreachable” to JSON and entry_type.

If unreachable is true, the instance is down.

src/json.cpp

@@ -1,5 +1,5 @@
 /*  This file is part of FediBlock-backend.
- *  Copyright © 2020 tastytea <tastytea@tastytea.de>
+ *  Copyright © 2020, 2021 tastytea <tastytea@tastytea.de>
  *
  *  This program is free software: you can redistribute it and/or modify
  *  it under the terms of the GNU Affero General Public License as published by
@@ -37,7 +37,8 @@ string to_json(const entry_type &entry)
                               {"receipts", entry.receipts},
                               {"description", entry.description},
                               {"screenshots", filenames},
-                              {"report_time", entry.report_time}};
+                              {"report_time", entry.report_time},
+                              {"unreachable", entry.unreachable}};
     // clang-format on
     return json.dump(4);
 }
@@ -81,6 +82,7 @@ entry_type from_json(const string_view json_string)
     {}
     entry.tags = json[0].at("tags").get<vector<string>>();
     entry.report_time = json[0].at("report_time").get<string>();
+    entry.unreachable = json[0].value("unreachable", false);
 
     return entry;
 }

src/types.hpp

@@ -35,6 +35,7 @@ struct entry_type
     vector<string> screenshot_filepaths;
     string report_time;
     string json_url;
+    bool unreachable{false};
 };
 
 enum class http_method