oracledb_cdc: Add support for snapshot_only mode, deprecating stream_snapshot config

[josephwoodward]

This change deprecates the stream_snapshot: (true|false) config in favour for snapshot_mode which supports a range of enums, including snapshot_only which allows users to launch the connector, perform a snapshot and then shutdown without it automatically switching to streaming. This makes it easier for new tables to be loaded.

snapshot_mode now includes:

• none (equivalent of stream_snapshot: false)
• snapshot_only (currently not representable in existing config)
• snapshot_and_stream (equivalent of stream_snapshot: true

[claude]

Commits

Message format is correct throughout (oracledb_cdc: <imperative>), and docs commits are kept separate from code. Two quality/granularity issues:

1. Typos that hurt readability:
   • oracledb_cdc: mode snapshot_mode config parsing to dedicated file — "mode" should be "move"; as written the message is hard to parse.
   • oracledb_cdc: update batching to ensure we exist loop first — "exist" should be "exit".
2. Vague WIP-style commits that should be squashed: clean up, tidy up config, tidy up benchmark config, update comments. These are iterative refinements of the same feature rather than self-contained logical changes, and the messages are too vague to convey intent.

Review

Reviewed the snapshot_mode addition to oracledb_cdc (config parsing + backward-compat, the snapshot-only stop path, and the batcher.go flush/shutdown changes) against the CDC connector standard, the Go patterns, and the test patterns.

LGTM — no code issues found. Notable points confirmed as correct:

• snapshot_mode enum (3 modes) is permitted by §5.3.1; stream_snapshot is retained and Deprecated() per §5.3.2; the SCN checkpoint is persisted as soon as the snapshot completes per §5.4.1.
• snapshot_mode is intentionally Optional() (no Default) so the stream_snapshot: true backward-compat fallback in parseSnapshotMode still fires; a static default would silently break existing configs.
• The batcher.go HardStopCtx/FlushRemaining/deferred-close changes and the snapshotOnlyDone + ErrEndOfInput path are internally consistent (final batch is delivered before TriggerHasStopped, no double-close, no deadlock with an active consumer).
• Config parsing is unit-tested and snapshot-only is exercised by the updated concurrent-snapshot integration test.

[claude]

Commits

A few message-quality issues (message quality is enforced); none block, but worth tidying before merge:

1. Vague messages that do not describe the change: oracledb_cdc: clean up and oracledb_cdc: tidy up config. State what was cleaned/tidied.
2. Typos: oracledb_cdc: mode snapshot_mode config parsing to dedicated file ("mode" → "move") and oracledb_cdc: update batching to ensure we exist loop first ("exist" → "exit").
3. The 15 commits are largely iterative fixups of a single feature (clean up / tidy up / update comments / update ctx handling). Consider squashing into a few self-contained logical commits. Documentation changes are already correctly isolated in their own commits (update docs, update snapshot_mode docs).

Review

Adds a snapshot_mode enum (none / snapshot_only / snapshot_and_stream) to oracledb_cdc, deprecating the boolean stream_snapshot. Reviewed against the §5 CDC Connector Standard and project Go patterns.

• Config naming conforms: snapshot_mode is the canonical enum name and the 3 modes justify it over a boolean (§5.3.1); stream_snapshot is kept accepted and marked Deprecated() with backward-compat precedence handled in parseSnapshotMode (§5.3.2).
• §5.4.1 satisfied: the SCN checkpoint is persisted as soon as the snapshot completes (input_oracledb_cdc.go:570), before the snapshot_only early-return.
• The FlushRemaining / HardStopCtx / snapshotOnlyDone shutdown path is sound: the loop is fully stopped before the final partial-batch flush, and ReadBatch returns ErrEndOfInput only after the final batch is handed off.
• Covered by an updated integration test (TestIntegrationOracleDBCDCConcurrentSnapshot now exercises snapshot_only) and a new TestParseSnapshotMode unit test including the backward-compat and precedence cases.

LGTM.