feat: support JSON2 row writes

[MichaelScofield]

Adds JSON2 ingestion through DataType.Json2, matching the Rust client’s native Protobuf encoding and schema metadata. JSON objects (including nested arrays and scalars) are accepted, top-level JSON null becomes SQL NULL, and invalid input is rejected before sending. The schema metadata supports automatic JSON2 table creation even when the first write contains only NULL.

• Upgrade greptimedb-proto to 0.16.0 and the CI integration server to GreptimeDB 1.2.1, including its renamed gRPC bind flag.
• Add a standalone Json2WriteQuickStart example using append_mode=true, plus encoding and JDBC round-trip coverage.
• Preserve existing JSON encoding and explicitly reject JSON2 in Bulk/Arrow writes.
• Validate decimal extensions before changing the schema builder, consistently across all data types.

Validation:

• Full Maven verification against official GreptimeDB 1.2.1 passed, including all 8 integration tests. Local JDK required -DargLine=--add-opens=java.base/java.nio=ALL-UNNAMED for Arrow.
• JSON2 integration coverage checks NULL-first auto-creation, nested data, changing field types, empty objects, JSON null, query results, and the JSON2 column type.
• TableSchemaTest and Json2Test passed after the final schema validation change.
• The example successfully inserted 5 rows against GreptimeDB 1.2.1.
• Repository-wide Spotless check and git diff --check passed.

[MichaelScofield]

@codex review

[chatgpt-codex-connector]

Codex Review Summary

This comment shows the latest Codex review activity on this pull request.

Review	Status	Commit	Review trigger
📝 Code Review	✅ Completed 2026-09-17T10:51:28.655396Z	879968e	Manual request

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[chatgpt-codex-connector]

Codex Review: Didn't find any major issues. Keep them coming!

Reviewed commit: 879968eddd

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[Copilot]

🟡 Changes recommended

Empty or whitespace-only JSON2 input is accepted as SQL NULL and must be rejected.

Get a fresh assessment by requesting another Copilot review.

Pull request overview

Adds native JSON2 ingestion for row writes, including Protobuf encoding, schema metadata, validation, tests, and a quickstart example.

Changes:

• Adds JSON2 parsing, encoding, and schema support.
• Rejects JSON2 in bulk/Arrow writes while preserving legacy JSON.
• Updates dependencies, CI, integration coverage, and documentation example.

File summaries

File	Summary
ingester-protocol/src/test/java/io/greptime/models/TableSchemaTest.java	Tests schema validation.
ingester-protocol/src/test/java/io/greptime/models/Json2Test.java	Tests JSON2 encoding and invalid input handling.
ingester-protocol/src/main/java/io/greptime/models/ValueUtil.java	Parses and encodes JSON2 values.
ingester-protocol/src/main/java/io/greptime/models/TableSchema.java	Adds JSON2 schema metadata and validation.
ingester-protocol/src/main/java/io/greptime/models/Table.java	Supports JSON2 column options.
ingester-protocol/src/main/java/io/greptime/models/RowHelper.java	Routes JSON2 row values.
ingester-protocol/src/main/java/io/greptime/models/DataType.java	Adds the Json2 data type.
ingester-protocol/src/main/java/io/greptime/models/ArrowHelper.java	Rejects JSON2 bulk writes.
ingester-protocol/pom.xml	Upgrades the protobuf dependency.
ingester-integration-tests/src/test/java/io/greptime/RegularWriteIT.java	Adds JSON2 integration coverage.
ingester-example/src/main/java/io/greptime/quickstart/write/Json2WriteQuickStart.java	Adds a JSON2 quickstart example.
.github/workflows/build.yml	Updates GreptimeDB CI configuration.

Review details

• Files reviewed: 12/12 changed files
• Comments generated: 1
• Review effort level: Lite

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[fengjiachun]

LGTM