How to write a configuration file for `.env` with the above structure `NotiferConfig`?

rust code:

#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct WebhookConfig {
    pub endpoint: String,
    pub auth_token: Option<String>,
    // pub custom_headers: Option<HashMap<String, String>>,
    pub max_retries: u32,
    pub timeout: u64,
}

// Configuration for the Kafka adapter.
#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct KafkaConfig {
    pub brokers: String,
    pub topic: String,
    pub max_retries: u32,
    pub timeout: u64,
}

/// Configuration for the MQTT adapter.
#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct MqttConfig {
    pub broker: String,
    pub port: u16,
    pub client_id: String,
    pub topic: String,
    pub max_retries: u32,
}

/// Configuration for the notification system.
#[derive(Debug, Clone, Serialize, Deserialize)]
#[serde(tag = "type")]
pub enum AdapterConfig {
    Webhook(WebhookConfig),
    Kafka(KafkaConfig),
    Mqtt(MqttConfig),
}

#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct NotifierConfig {
    #[serde(default = "default_store_path")]
    pub store_path: String,
    #[serde(default = "default_channel_capacity")]
    pub channel_capacity: usize,
    pub adapters: Vec<AdapterConfig>,
}

toml file:

# config.toml
store_path = "/var/log/event-notifier"
channel_capacity = 5000

[[adapters]]
type = "Webhook"
endpoint = "https://api.example.com/webhook/toml"
auth_token = "your-auth-token"
max_retries = 3
timeout = 50

[adapters.0.custom_headers]
X-Custom = "value"

[[adapters]]
type = "Kafka"
brokers = "localhost:9092"
topic = "notifications"
max_retries = 3
timeout = 60

[[adapters]]
type = "Mqtt"
broker = "mqtt.example.com"
port = 1883
client_id = "event-notifier"
topic = "events"
max_retries = 3

env file:

# Global config
NOTIFIER_STORE_PATH=/var/log/event-notification
NOTIFIER_CHANNEL_CAPACITY=5000

# Adapters (array)
NOTIFIER_ADAPTERS_0_TYPE=Webhook
NOTIFIER_ADAPTERS_0_ENDPOINT=https://api.example.com/webhook
NOTIFIER_ADAPTERS_0_AUTH_TOKEN=your-token
NOTIFIER_ADAPTERS_0_MAX_RETRIES=3
NOTIFIER_ADAPTERS_0_TIMEOUT=50

NOTIFIER_ADAPTERS_1_TYPE=Kafka
NOTIFIER_ADAPTERS_1_BROKERS=localhost:9092
NOTIFIER_ADAPTERS_1_TOPIC=notifications
NOTIFIER_ADAPTERS_1_MAX_RETRIES=3
NOTIFIER_ADAPTERS_1_TIMEOUT=60

NOTIFIER_ADAPTERS_2_TYPE=Mqtt
NOTIFIER_ADAPTERS_2_BROKER=mqtt.example.com
NOTIFIER_ADAPTERS_2_PORT=1883
NOTIFIER_ADAPTERS_2_CLIENT_ID=event-notifier
NOTIFIER_ADAPTERS_2_TOPIC=events
NOTIFIER_ADAPTERS_2_MAX_RETRIES=3

read .env file error：

Failed to deserialize config: invalid type: map, expected a sequence for key `adapters`

# Global config
NOTIFIER_STORE_PATH=/var/log/event-notification
NOTIFIER_CHANNEL_CAPACITY=5000

# Adapters (array)
NOTIFIER_ADAPTERS_0__TYPE=Webhook
NOTIFIER_ADAPTERS_0__ENDPOINT=https://api.example.com/webhook
NOTIFIER_ADAPTERS_0__AUTH_TOKEN=your-token
NOTIFIER_ADAPTERS_0__MAX_RETRIES=3
NOTIFIER_ADAPTERS_0__TIMEOUT=50

NOTIFIER_ADAPTERS_1__TYPE=Kafka
NOTIFIER_ADAPTERS_1__BROKERS=localhost:9092
NOTIFIER_ADAPTERS_1__TOPIC=notifications
NOTIFIER_ADAPTERS_1__MAX_RETRIES=3
NOTIFIER_ADAPTERS_1__TIMEOUT=60

NOTIFIER_ADAPTERS_2__TYPE=Mqtt
NOTIFIER_ADAPTERS_2__BROKER=mqtt.example.com
NOTIFIER_ADAPTERS_2__PORT=1883
NOTIFIER_ADAPTERS_2__CLIENT_ID=event-notifier
NOTIFIER_ADAPTERS_2__TOPIC=events
NOTIFIER_ADAPTERS_2__MAX_RETRIES=3

read .env file error：

Failed to deserialize config: missing field `adapters`

#631 #536 @epage

No repository file or test is named. Start by tracing environment-source deserialization for the NotifierConfig adapters Vec and compare it with the TOML representation. Done means the expected environment-variable format is documented or supported consistently, with a regression test if the behavior is intended.