This pull request introduces support for HTTP transport.

QuestDB ILP client supports HTTP transport in versions 7.4.0+ thus the client dependency version is updated too.

Configuration
The connector now supports client configuration strings as documented in the client documentation. Set the client configuration string under the key client.conf.string.

Example:

{
  "name": "my-connector",
  "config": {
    "tasks.max": "4",
    "connector.class": "io.questdb.kafka.QuestDBSinkConnector",
    "key.converter": "org.apache.kafka.connect.storage.StringConverter",
    "value.converter": "org.apache.kafka.connect.json.JsonConverter",
    "topics": "mytopic",
    "value.converter.schemas.enable": "false",
    "timestamp.field.name": "ts",
    "timestamp.units": "nanos",
    "client.conf.string": "http::addr=questdb:9000;auto_flush_rows=10000;auto_flush_interval=1200000;retry_timeout=60000;"
  }
}

The old client configuration keys (host, username, token, tls, etc) are considered deprecated and should not be used. They cannot be used together with the client configuration string.

Kafka-specific configuration options (timestamp.units, topics, etc.) are not part of the client configuration string and still have their own keys. See the example above.

Advantages of the HTTP transport
The HTTP transport implements proper error reporting, automatic retries for recoverable errors and simpler configuration. When combined with QuestDB server deduplications it allows Exactly-Once semantics.

Known Issues
Due to a bug in QuestDB client 7.4.0 it's recommended to disable interval-based flushes. See questdb/questdb#4372 for details. This will be resolved in the next version.