add: Rate limiting & tests

internal/config/config.go

@@ -48,6 +48,12 @@ type RecipientsConfig struct {
 	UserRegistration string `json:"UserRegistration" envconfig:"RECIPIENT_USER_REGISTRATION"`
 }
 
+type SecurityConfig struct {
+	Ratelimits struct {
+		Limit int `json:"Limit" default:"1" envconfig:"RATE_LIMIT"`
+		Burst int `json:"Burst" default:"60" envconfig:"BURST_LIMIT"`
+	} `json:"RateLimits"`
+}
 type Config struct {
 	Auth           AuthenticationConfig `json:"auth"`
 	Templates      TemplateConfig       `json:"templates"`
@@ -56,6 +62,7 @@ type Config struct {
 	BaseURL        string               `json:"BaseUrl" envconfig:"BASE_URL"`
 	DB             DatabaseConfig       `json:"db"`
 	SMTP           SMTPConfig           `json:"smtp"`
+	Security       SecurityConfig       `json:"security"`
 }
 
 var (
@@ -67,6 +74,7 @@ var (
 	Templates  TemplateConfig
 	SMTP       SMTPConfig
 	Recipients RecipientsConfig
+	Security   SecurityConfig
 )
 
 // LoadConfig initializes the configuration by reading from a file and environment variables.
@@ -94,6 +102,7 @@ func LoadConfig() {
 	SMTP = CFG.SMTP
 	BaseURL = CFG.BaseURL
 	Recipients = CFG.Recipients
+	Security = CFG.Security
 }
 
 // readFile reads the configuration from the specified file path into the provided Config struct.