Redact database URL passwords from logs

- Add SanitizeDatabaseURL() function to config package that redacts passwords from database connection URLs
- Handles various URL formats: postgresql, mysql, etc.
- Correctly handles passwords containing special characters including @ symbols by using LastIndex
- Update startup logging in cmd/server/main.go to use sanitized database URL
- Add comprehensive tests covering various URL formats and edge cases

This ensures sensitive database credentials are not exposed in application logs.

internal/config/config.go

@@ -418,6 +418,9 @@ func (c *Config) Sanitize() map[string]interface{} {
 	// Sanitize auth config
 	sanitized["auth"] = map[string]interface{}{
 		"enabled": c.Auth.Enabled,
+		"database": map[string]interface{}{
+			"url": SanitizeDatabaseURL(c.Auth.Database.URL),
+		},
 		"bootstrap": map[string]interface{}{
 			"enabled":                c.Auth.Bootstrap.Enabled,
 			"admin_key_file":         c.Auth.Bootstrap.AdminKeyFileName,
@@ -438,6 +441,47 @@ func (c *Config) Sanitize() map[string]interface{} {
 	return sanitized
 }
 
+// SanitizeDatabaseURL redacts the password from a database connection URL
+// Handles formats like: postgresql://user:password@host:port/database
+// Also handles passwords containing @ characters by finding the last @
+func SanitizeDatabaseURL(dbURL string) string {
+	if dbURL == "" {
+		return ""
+	}
+
+	// Find the protocol (e.g., "postgresql://", "mysql://")
+	protocolIdx := strings.Index(dbURL, "://")
+	if protocolIdx == -1 {
+		return dbURL
+	}
+
+	protocol := dbURL[:protocolIdx+3]
+	remaining := dbURL[protocolIdx+3:]
+
+	// Find the LAST @ symbol that separates credentials from host
+	// (to handle passwords that may contain @ characters)
+	atIdx := strings.LastIndex(remaining, "@")
+	if atIdx == -1 {
+		// No credentials in the URL
+		return dbURL
+	}
+
+	// Extract credentials part and check if there's a password
+	credentials := remaining[:atIdx]
+	hostPart := remaining[atIdx:]
+
+	// Check if there's a colon (indicating a password)
+	colonIdx := strings.Index(credentials, ":")
+	if colonIdx == -1 {
+		// No password, just username
+		return protocol + credentials + hostPart
+	}
+
+	// Extract username and redact password
+	username := credentials[:colonIdx]
+	return protocol + username + ":***REDACTED***" + hostPart
+}
+
 // GetDefaultAccount returns the default account name for a notifier type, or the first account if no default is set
 func (c *Config) GetDefaultAccount(notifierType domain.NotificationType) string {
 	switch notifierType {

internal/config/config_test.go

@@ -0,0 +1,63 @@
+package config
+
+import (
+	"testing"
+)
+
+func TestSanitizeDatabaseURL(t *testing.T) {
+	tests := []struct {
+		name     string
+		input    string
+		expected string
+	}{
+		{
+			name:     "PostgreSQL with password",
+			input:    "postgresql://user:password@localhost:5432/dbname",
+			expected: "postgresql://user:***REDACTED***@localhost:5432/dbname",
+		},
+		{
+			name:     "PostgreSQL without password",
+			input:    "postgresql://user@localhost:5432/dbname",
+			expected: "postgresql://user@localhost:5432/dbname",
+		},
+		{
+			name:     "MySQL with special characters in password",
+			input:    "mysql://root:SuperSecret123!@db.example.com:3306/mydb",
+			expected: "mysql://root:***REDACTED***@db.example.com:3306/mydb",
+		},
+		{
+			name:     "Empty URL",
+			input:    "",
+			expected: "",
+		},
+		{
+			name:     "Invalid URL without protocol",
+			input:    "invalid-url",
+			expected: "invalid-url",
+		},
+		{
+			name:     "URL without credentials",
+			input:    "postgresql://localhost:5432/dbname",
+			expected: "postgresql://localhost:5432/dbname",
+		},
+		{
+			name:     "PostgreSQL with password containing colons",
+			input:    "postgresql://user:pass:word@localhost:5432/dbname",
+			expected: "postgresql://user:***REDACTED***@localhost:5432/dbname",
+		},
+		{
+			name:     "PostgreSQL with complex hostname and port",
+			input:    "postgresql://admin:p@ssw0rd!@db-prod.example.com:5432/production",
+			expected: "postgresql://admin:***REDACTED***@db-prod.example.com:5432/production",
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			result := SanitizeDatabaseURL(tt.input)
+			if result != tt.expected {
+				t.Errorf("SanitizeDatabaseURL(%q) = %q, want %q", tt.input, result, tt.expected)
+			}
+		})
+	}
+}