Store errors as strings to speed up compilation

include/mtx/responses/crypto.hpp

@@ -35,7 +35,7 @@ struct QueryKeys
     //! If any remote homeservers could not be reached, they are
     //! recorded here. The names of the properties are the names
     //! of the unreachable servers.
-    std::map<std::string, nlohmann::json> failures;
+    std::map<std::string, std::string> failures;
     //! Information on the queried devices.
     //! A map from user ID, to a map from device ID to device information.
     //! For each device, the information returned will be the same
@@ -67,7 +67,7 @@ struct ClaimKeys
     //! If any remote homeservers could not be reached, they are
     //! recorded here. The names of the properties are the names
     //! of the unreachable servers.
-    std::map<std::string, nlohmann::json> failures;
+    std::map<std::string, std::string> failures;
     //! One-time keys for the queried devices. A map from user ID,
     //! to a map from <algorithm>:<key_id> to the key object.
     std::map<std::string, std::map<std::string, nlohmann::json>> one_time_keys;

lib/structs/responses/crypto.cpp

@@ -15,8 +15,11 @@ from_json(const nlohmann::json &obj, UploadKeys &response)
 void
 from_json(const nlohmann::json &obj, QueryKeys &response)
 {
-    if (obj.contains("failures"))
-        response.failures = obj.at("failures").get<std::map<std::string, nlohmann::json>>();
+    if (obj.contains("failures")) {
+        for (const auto &[key, value] :
+             obj.at("failures").get<std::map<std::string, nlohmann::json>>())
+            response.failures[key] = value.dump();
+    }
     if (obj.contains("device_keys"))
         response.device_keys = obj.at("device_keys").get<std::map<std::string, DeviceToKeysMap>>();
     if (obj.contains("master_keys"))
@@ -33,7 +36,9 @@ from_json(const nlohmann::json &obj, QueryKeys &response)
 void
 to_json(nlohmann::json &obj, const QueryKeys &response)
 {
-    obj["failures"]          = response.failures;
+    for (const auto &[key, value] : response.failures)
+        obj["failures"][key] = nlohmann::json::parse(value);
+
     obj["device_keys"]       = response.device_keys;
     obj["master_keys"]       = response.master_keys;
     obj["user_signing_keys"] = response.user_signing_keys;
@@ -50,8 +55,11 @@ from_json(const nlohmann::json &obj, KeySignaturesUpload &response)
 void
 from_json(const nlohmann::json &obj, ClaimKeys &response)
 {
-    if (obj.contains("failures"))
-        response.failures = obj.at("failures").get<std::map<std::string, nlohmann::json>>();
+    if (obj.contains("failures")) {
+        for (const auto &[key, value] :
+             obj.at("failures").get<std::map<std::string, nlohmann::json>>())
+            response.failures[key] = value.dump();
+    }
     if (obj.contains("one_time_keys"))
         response.one_time_keys =
           obj.at("one_time_keys")