Implement /ignore and /unignore commands

Simplify authorized network requests for Twitch V5 api
add onShow virtual function to settings pages if they need to be refreshed when shown
Actually ignoring messages from ignored users is still not implemented

Working on #247

src/providers/twitch/twitchuser.cpp

@@ -0,0 +1,34 @@
+#include "providers/twitch/twitchuser.hpp"
+
+#include "util/rapidjson-helpers.hpp"
+
+namespace chatterino {
+namespace providers {
+namespace twitch {
+
+TwitchUser TwitchUser::fromJSON(const rapidjson::Value &value)
+{
+    TwitchUser user;
+
+    if (!value.IsObject()) {
+        throw std::runtime_error("JSON value is not an object");
+    }
+
+    if (!rj::getSafe(value, "_id", user.id)) {
+        throw std::runtime_error("Missing ID key");
+    }
+
+    if (!rj::getSafe(value, "name", user.name)) {
+        throw std::runtime_error("Missing name key");
+    }
+
+    if (!rj::getSafe(value, "display_name", user.displayName)) {
+        throw std::runtime_error("Missing display name key");
+    }
+
+    return user;
+}
+
+}  // namespace twitch
+}  // namespace providers
+}  // namespace chatterino