Add multithreaded logging infrastructure for preparation for future designs (#225)

* Update class diagrams

* Implement BoundedChannel and multithreaded logging infra

* Integrate logging channel system

* Update string concatenations to use std::format

* Add pretty print log

tooling/pipeline/src/services/logging/log_dispatcher.cc

@@ -0,0 +1,74 @@
+/**
+ * @brief LogDispatcher implementation for asynchronous pipeline logging.
+ *
+ * LogDispatcher drains LogEntry items from a BoundedChannel and forwards them
+ * to spdlog for final output.
+ */
+#include "services/logging/log_dispatcher.h"
+
+#include <spdlog/spdlog.h>
+
+#include <string>
+
+#include "concurrency/bounded_channel.h"
+#include "services/logging/log_entry.h"
+
+namespace {
+[[nodiscard]] constexpr std::string_view PipelinePhaseToString(
+    PipelinePhase phase) {
+  switch (phase) {
+    case PipelinePhase::Startup:
+      return "Startup";
+    case PipelinePhase::UserGeneration:
+      return "User Generation";
+    case PipelinePhase::BreweryAndBeerGeneration:
+      return "Brewery & Beer Gen";
+    case PipelinePhase::CheckinGeneration:
+      return "Checkin Gen";
+    case PipelinePhase::RatingGeneration:
+      return "Rating Gen";
+    case PipelinePhase::FollowGeneration:
+      return "Follow Gen";
+    case PipelinePhase::Teardown:
+      return "Teardown";
+  }
+  return "Unknown";
+}
+}  // namespace
+
+LogDispatcher::LogDispatcher(BoundedChannel<LogEntry>& channel)
+    : channel_(channel) {}
+
+void LogDispatcher::Run() {
+  auto logger = spdlog::default_logger();
+
+  while (true) {
+    auto entry = channel_.Receive();
+    if (!entry.has_value()) {
+      // Channel is closed and drained.
+      break;
+    }
+
+    const auto& log = entry.value();
+
+    logger->log(ToSpdlogLevel(log.level),
+                "{:<20} │ thread: {:016x} │ [{}:{}] │ {}",
+                PipelinePhaseToString(log.phase),
+                std::hash<std::thread::id>{}(log.thread_id),
+                log.origin.file_name(), log.origin.line(), log.message);
+  }
+}
+
+spdlog::level::level_enum LogDispatcher::ToSpdlogLevel(LogLevel level) {
+  switch (level) {
+    case LogLevel::Debug:
+      return spdlog::level::debug;
+    case LogLevel::Info:
+      return spdlog::level::info;
+    case LogLevel::Warn:
+      return spdlog::level::warn;
+    case LogLevel::Error:
+      return spdlog::level::err;
+  }
+  return spdlog::level::info;
+}