Gtest IT: log also to stderr, not only to file (#461)

## Motivation

[A recent CI
run](https://github.com/scylladb/cpp-rs-driver/actions/runs/26300848077/job/77426773254?pr=456)
experienced a panic inside the Rust Driver. I couldn't debug it, because
no logs were printed.

## What's done

### C++ Gtest Logger output

#### Destination

Before, the logs were only output to a file. Now, they are additionally
printed to stderr.

#### Format

1. Timestamp display was improved, made in line with Rust tracing
subscriber's one.
2. Log level is now coloured (IFF stderr points to a terminal). It uses
the same palette as, again, Rust tracing subscriber.

### CI

1. `RUST_LOG=trace` is now passed, so the logs are visible in the CI run
console.
2. `RUST_BACKTRACE=full` is now passed, which will aid in debugging.

Author: wprzytula

.github/workflows/build-lint-and-test.yml

@@ -8,6 +8,8 @@ on:
 
 env:
   CARGO_TERM_COLOR: always
+  RUST_BACKTRACE: full
+  RUST_LOG: trace
   # Should include `INTEGRATION_TEST_BIN` from the `Makefile`
   # TODO: Remove `build/libscylla-cpp-driver.*` after https://github.com/scylladb/cpp-rs-driver/issues/164 is fixed.
   INTEGRATION_TEST_BIN: |

MAINTENANCE.md

@@ -5,7 +5,7 @@ other information / procedures useful for maintainers. It is heavily inspired by
 
 ## Documentation
 
-TODO (no docs written yet)
+Comprehensive Sphinx-compatible documentation lives at /docs.
 Note: Due to API compatibility, cpp-driver docs apply to cpp-rs-driver in general. Though, some discrepancies should be well-documented in cpp-rs-driver (some of them are already mentioned in `cassandra.h`).
 
 ## Version bump commit

tests/src/integration/logger.cpp

@@ -32,9 +32,15 @@ using namespace test::driver;
 #ifdef _WIN32
 #define FILE_MODE 0
 #define LOCALTIME(tm, time) localtime_s(tm, time)
+#define GMTIME(tm, time) gmtime_s(tm, time)
+#include <io.h>
+#define IS_STDERR_TTY() _isatty(_fileno(stderr))
 #else
 #define FILE_MODE S_IRWXU | S_IRWXG | S_IROTH
 #define LOCALTIME(tm, time) localtime_r(time, tm)
+#define GMTIME(tm, time) gmtime_r(time, tm)
+#include <unistd.h>
+#define IS_STDERR_TTY() isatty(STDERR_FILENO)
 #endif
 
 Logger::Logger()
@@ -125,7 +131,34 @@ void Logger::log(const CassLogMessage* log, void* data) {
   // Create the formatted log message and output to the file
   std::string severity = cass_log_level_string(log->severity);
   logger->output_ << date.str() << " " << time.str() << " " << severity << ": " << message << " ("
-                  << log->file << ":" << log->line << ") " << std::endl;
+                   << log->file << ":" << log->line << ") " << std::endl;
+
+  // Also log to stderr so that CI output captures driver logs in real-time.
+  static bool use_color = IS_STDERR_TTY();
+  const char* color = "";
+  const char* reset = "";
+  const char* dim = "";
+  if (use_color) {
+    reset = "\033[0m";
+    dim = "\033[2m";
+    switch (log->severity) {
+      case CASS_LOG_TRACE: color = "\033[35m"; break;
+      case CASS_LOG_DEBUG: color = "\033[34m"; break;
+      case CASS_LOG_INFO: color = "\033[32m"; break;
+      case CASS_LOG_WARN: color = "\033[33m"; break;
+      default: color = "\033[31m"; break;
+    }
+  }
+  cass_uint64_t const epoch_secs = log->time_ms / 1000;
+  unsigned short const ms = log->time_ms % 1000;
+  time_t const raw = static_cast<time_t>(epoch_secs);
+  struct tm utc;
+  GMTIME(&utc, &raw);
+  char ts[24];
+  strftime(ts, sizeof(ts), "%Y-%m-%dT%H:%M:%S", &utc);
+  std::cerr << ts << "." << std::setfill('0') << std::setw(3) << ms << "Z" << " [" << color << severity << reset << "] "
+            << dim << "(" << log->file << ":" << log->line << ")" << reset
+            << " " << message << std::endl;
 
   // Determine if the log message matches any of the criteria
   for (std::vector<std::string>::const_iterator iterator = logger->search_criteria_.begin();