[client-v2] Expose supported configuration options via a public API

client-v2 の ClientConfigProperties enum と jdbc-v2 の Driver.getPropertyInfo(url, info) エントリーポイントから始め、現在のキー、型、デフォルト値がどのように定義されているかを追跡します。完了時には plain client-v2 用の構造化メタデータを提供し、動的なプレフィックスと要求されたフラグをカバーし、JDBC のプロパティ情報の一貫性を維持する必要があります。

Is your feature request related to a problem?

Connectors and tools built on top of the Java client (e.g. Kafka Connect sink, Spark connector, ingestion frameworks, config-validation UIs) need to know which configuration options the client supports so they can expose, validate, and document them programmatically. Today there is no supported API call to retrieve this list:

• ClientConfigProperties (client-v2) is a public enum, but it only carries the option key, value type, and default value — no human-readable description, no allowed-value/choices metadata, and no indication of whether an option is required or deprecated.
• jdbc-v2 implements Driver.getPropertyInfo(url, info) returning DriverPropertyInfo[], but that is JDBC-specific and not usable from plain client-v2.

Describe the solution you'd like

A public API on the client (e.g. Client.getSupportedOptions() or a static method on ClientConfigProperties) that returns structured metadata for every supported option:

• option key (e.g. connect_timeout)
• value type
• default value
• description
• allowed values / choices where applicable
• flags such as required, deprecated, sensitive (e.g. password, so tools know to mask it)

This would let integrators generate their config surface directly from the client instead of hard-coding option lists that drift out of date. Ideally jdbc-v2's getPropertyInfo would be backed by the same metadata source so the two stay consistent.

Describe alternatives you've considered

• Iterating ClientConfigProperties.values() via the enum — works for key/type/default but lacks descriptions and semantic metadata, and does not cover dynamic prefixes (clickhouse_setting_*, http_header_*).
• Scraping the docs — brittle and not machine-friendly.