feat: implement admin and OIDC authentication methods; add login and user info endpoints

Signed-off-by: Noste <83548733+Noooste@users.noreply.github.com>

backend/pkg/utils/retry.go

@@ -0,0 +1,104 @@
+package utils
+
+import (
+	"context"
+	"errors"
+	"fmt"
+	"net"
+	"syscall"
+	"time"
+)
+
+// RetryConfig configures retry behavior
+type RetryConfig struct {
+	MaxRetries     int
+	InitialBackoff time.Duration
+	MaxBackoff     time.Duration
+	BackoffFactor  float64
+}
+
+// DefaultRetryConfig returns default retry configuration
+func DefaultRetryConfig() RetryConfig {
+	return RetryConfig{
+		MaxRetries:     3,
+		InitialBackoff: 100 * time.Millisecond,
+		MaxBackoff:     5 * time.Second,
+		BackoffFactor:  2.0,
+	}
+}
+
+// IsConnectionRefused checks if the error is a connection refused error
+func IsConnectionRefused(err error) bool {
+	if err == nil {
+		return false
+	}
+
+	// Check for connection refused error
+	var opErr *net.OpError
+	if errors.As(err, &opErr) {
+		// Check if it's a connection refused error
+		if opErr.Op == "dial" || opErr.Op == "read" {
+			var syscallErr *syscall.Errno
+			if errors.As(opErr.Err, &syscallErr) {
+				return *syscallErr == syscall.ECONNREFUSED
+			}
+		}
+	}
+
+	// Also check for "connection refused" in error message as fallback
+	if errors.Is(err, syscall.ECONNREFUSED) {
+		return true
+	}
+
+	return false
+}
+
+// RetryWithBackoff executes a function with exponential backoff on connection refused errors
+func RetryWithBackoff(ctx context.Context, config RetryConfig, fn func() error) error {
+	var lastErr error
+
+	for attempt := 0; attempt <= config.MaxRetries; attempt++ {
+		// Execute the function
+		err := fn()
+		if err == nil {
+			return nil
+		}
+
+		lastErr = err
+
+		// If it's not a connection refused error, don't retry
+		if !IsConnectionRefused(err) {
+			return err
+		}
+
+		// If this was the last attempt, return the error
+		if attempt == config.MaxRetries {
+			return fmt.Errorf("max retries (%d) exceeded: %w", config.MaxRetries, err)
+		}
+
+		// Calculate backoff duration with exponential increase
+		backoff := time.Duration(float64(config.InitialBackoff) * pow(config.BackoffFactor, float64(attempt)))
+		if backoff > config.MaxBackoff {
+			backoff = config.MaxBackoff
+		}
+
+		// Wait with context cancellation support
+		select {
+		case <-ctx.Done():
+			return fmt.Errorf("context cancelled during retry: %w", ctx.Err())
+		case <-time.After(backoff):
+			// Continue to next attempt
+		}
+	}
+
+	return lastErr
+}
+
+// pow is a simple integer exponentiation helper
+func pow(base float64, exp float64) float64 {
+	result := 1.0
+	for i := 0; i < int(exp); i++ {
+		result *= base
+	}
+	return result
+}