* fix(replication): resume partial chunk reads on EOF instead of re-downloading
When replicating chunks and the source connection drops mid-transfer,
accumulate the bytes already received and retry with a Range header
to fetch only the remaining bytes. This avoids re-downloading
potentially large chunks from scratch on each retry, reducing load
on busy source servers and speeding up recovery.
* test(replication): add tests for downloadWithRange including gzip partial reads
Tests cover:
- No offset (no Range header sent)
- With offset (Range header verified)
- Content-Disposition filename extraction
- Partial read + resume: server drops connection mid-transfer, client
resumes with Range from the offset of received bytes
- Gzip partial read + resume: first response is gzip-encoded (Go auto-
decompresses), connection drops, resume request gets decompressed data
(Go doesn't add Accept-Encoding when Range is set, so the server
decompresses), combined bytes match original
* fix(replication): address PR review comments
- Consolidate downloadWithRange into DownloadFile with optional offset
parameter (variadic), eliminating code duplication (DRY)
- Validate HTTP response status: require 206 + correct Content-Range
when offset > 0, reject when server ignores Range header
- Use if/else for fullData assignment for clarity
- Add test for rejected Range (server returns 200 instead of 206)
* refactor(replication): remove unused ReplicationSource interface
The interface was never referenced and its signature didn't match
the actual FilerSource.ReadPart method.
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Co-authored-by: Copilot <copilot@github.com>
