db/config, utils: allow using UUID as a config option

We change the `recovery_leader` option to UUID in the following commit.

db/config.cc

@@ -86,6 +86,12 @@ object_storage_endpoints_to_json(const std::vector<db::object_storage_endpoint_p
     return value_to_json(m);
 }
 
+static
+json::json_return_type
+uuid_to_json(const db::config::UUID& uuid) {
+    return value_to_json(format("{}", uuid));
+}
+
 // Convert a value that can be printed with fmt::format, or a vector of
 // such values, to JSON. An example is enum_option<T>, because enum_option<T>
 // has a specialization for fmt::formatter.
@@ -294,6 +300,12 @@ const config_type& config_type_for<std::vector<db::object_storage_endpoint_param
     return ct;
 }
 
+template <>
+const config_type& config_type_for<db::config::UUID>() {
+    static config_type ct("UUID", uuid_to_json);
+    return ct;
+}
+
 }
 
 namespace YAML {
@@ -491,6 +503,22 @@ struct convert<db::object_storage_endpoint_param> {
     }
 };
 
+template<>
+struct convert<utils::UUID> {
+    static bool decode(const Node& node, utils::UUID& uuid) {
+        std::string uuid_string;
+        if (!convert<std::string>::decode(node, uuid_string)) {
+            return false;
+        }
+        try {
+            std::istringstream(uuid_string) >> uuid;
+        } catch (boost::program_options::invalid_option_value&) {
+            return false;
+        }
+        return true;
+    }
+};
+
 }
 
 #if defined(DEBUG)

db/config.hh

@@ -207,6 +207,7 @@ public:
     using seed_provider_type = db::seed_provider_type;
     using hinted_handoff_enabled_type = db::hints::host_filter;
     using error_injection_at_startup = db::error_injection_at_startup;
+    using UUID = utils::UUID;
 
     /*
      * All values and documentation taken from

utils/UUID.hh

@@ -68,6 +68,8 @@ public:
 
     friend std::ostream& operator<<(std::ostream& out, const UUID& uuid);
 
+    friend std::istream& operator>>(std::istream& in, UUID& uuid);
+
     bool operator==(const UUID& v) const noexcept = default;
 
     // Please note that this comparator does not preserve timeuuid

utils/uuid.cc

@@ -38,6 +38,13 @@ std::ostream& operator<<(std::ostream& out, const UUID& uuid) {
     return out;
 }
 
+std::istream& operator>>(std::istream& in, UUID& uuid) {
+    sstring uuid_string;
+    in >> uuid_string;
+    uuid = UUID(uuid_string);
+    return in;
+}
+
 UUID::UUID(std::string_view uuid) {
     sstring uuid_string(uuid.begin(), uuid.end());
     boost::erase_all(uuid_string, "-");