feat: Add C bindings for DynamoDB Big Segments store

[beekld]

Summary

Adds a C binding for DynamoDBBigSegmentStore so C callers can wire the existing DynamoDB Big Segments integration into the SDK's Big Segments config.

New public surface:

• LDServerBigSegmentsDynamoDBStore opaque handle.
• struct LDServerBigSegmentsDynamoDBResult with store and error_message fields.
• LDSERVER_BIGSEGMENTS_DYNAMODBSTORE_ERROR_MESSAGE_SIZE macro.
• LDServerBigSegmentsDynamoDBStore_New(table_name, prefix, options, out_result) factory.
• LDServerBigSegmentsDynamoDBStore_Free(store).

Tests:

• Unit tests for successful creation with and without the options builder (NULL means "AWS SDK default provider chain").
• End-to-end test against DynamoDB Local: primes a sync timestamp via PrefixedDynamoDBClient::PutBigSegmentSyncTime, wires the store through the C API, and verifies the SDK reports the store available via the Big Segment status listener.

The type name uses config-section-first word order (BigSegments + DynamoDB + Store), matching the sibling Redis Big Segments binding LDServerBigSegmentsRedisStore (#574) and the sibling DynamoDB LazyLoad binding LDServerLazyLoadDynamoDBSource (#576). The options parameter reuses the LDServerDynamoDBClientOptionsBuilder introduced in #576.

Stacked on #576 (DynamoDB LazyLoad source). Please review that PR first.

---

Note

Low Risk
New C API surface and tests only; behavior delegates to existing DynamoDBBigSegmentStore::Create with no changes to core evaluation or auth paths.

Overview
Exposes the existing DynamoDB Big Segments integration to C callers via a new public header and thin C++ shim, aligned with LDServerBigSegmentsRedisStore and the DynamoDB LazyLoad C API.

LDServerBigSegmentsDynamoDBStore_New takes table name, prefix, and optional LDServerDynamoDBClientOptionsBuilder (NULL uses the AWS default provider chain; non-NULL builder is consumed on entry). Results land in LDServerBigSegmentsDynamoDBResult (store + fixed-size error_message). LDServerBigSegmentsDynamoDBStore_Free is for callers who do not hand ownership to LDServerBigSegmentsBuilder.

The dynamodb-source library build now compiles bindings/dynamodb/dynamodb_big_segment_store.cpp. C binding tests cover creation with/without options, partial-credentials rejection, and a DynamoDB Local E2E path that wires the store into the SDK and asserts Big Segment store status becomes available. Comment typos (Explicitely → Explicitly) are fixed in related Redis/DynamoDB binding files.

^{Reviewed by Cursor Bugbot for commit 8978c77. Bugbot is set up for automated code reviews on this repo. Configure here.}

[kinyoklion]

I think we will need stdbool. Which also means we are missing some test case. Or maybe we transiently get stdbool? But it makes me nervous.

[beekld]

Not missing test cases, but all of our tests are written in C++, not C. The only coverage we have of this is the example files. gtest is C++ so I can't easily convert them. I filed a task to follow up on this and maybe add some pure C compilation tasks. But that's a bigger task than I wanna put in this PR.

[kinyoklion]

Typo, but likely a copy/paste typo?

[beekld]

Fixed here and in the places it was copy-pasted from.

[cursor]

Cursor Bugbot has reviewed your changes using default effort and found 2 potential issues.

^{❌ Bugbot Autofix is OFF. To automatically fix reported issues with cloud agents, have a team admin enable autofix in the Cursor dashboard.}

^{Reviewed by Cursor Bugbot for commit 204affd. Configure here.}