feat(go): add TransformationOptions for ingestion transporter configuration

[MarioAlexandruDan]

🧭 What and Why

Part of the effort to standardize transformationOptions across all 11 language SDKs. Depends on the JS + Foundation ticket for CTS infrastructure.

🎟 JIRA Ticket API-374:

Changes included:

• TransformationOptions fields are flat: Go has no general-purpose ClientOptions primitive, so duplicating 6 fields directly avoids a single-use wrapper.
• ClientOption func(SearchConfiguration) functional option: Go's idiomatic way to pass optional construction-time config; WithTransformationOptions(opts) fits naturally alongside other future With options.
• SetTransformationOptions also exposed as a method: Lets callers configure after construction without rebuilding the client, consistent with SetClientApiKey.
• DefaultHeader direct assignment, not merge: In Go, auth headers are injected per-request from cfg.AppID/cfg.ApiKey, not stored in DefaultHeader, so replacing it doesn't wipe credentials.
• transformation_options.mustache registered only for search client: Only the search client needs the transporter helpers; conditional registration avoids generating a useless file for every other client.

🧪 Test

[algolia-bot]

✔️ Code generated!

Name	Link
🪓 Triggered by	77cd42381d9650fba5ded6b77442564d1643410d
🍃 Generated commit	96ccc364fe00dc35c51e0e2402c3382daaef6b1c
🌲 Generated branch	generated/feat/go-transformation-options

📊 Benchmark results

Benchmarks performed on the method using a mock server, the results might not reflect the real-world performance.

Language	Req/s
go	2331
javascript	2290
php	2036
csharp	1516
python	1233
java	1105
ruby	905
swift	512
scala	23

[codacy-production]

Up to standards ✅

🟢 Issues 0 issues

Results:
0 new issues

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