Add function chains support for search

[yhmo]

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[Copilot]

Pull request overview

This PR adds a new “function chain” API surface to the C++ SDK and wires it into SearchRequest serialization, enabling server-side post-processing pipelines (e.g., map/sort/limit) to be attached to search requests.

Changes:

• Introduces new milvus::FunctionChain* types (stage/ops/expressions) and a fluent builder API.
• Extends milvus::SearchRequest to carry function chains and enforces mutual exclusion with rerank in Validate().
• Serializes function chains into the RPC search request and adds unit tests for the builder/request behavior.

Reviewed changes

Copilot reviewed 8 out of 8 changed files in this pull request and generated 4 comments.

Show a summary per file

File	Description
test/ut/types/TestFunctionChain.cpp	Adds unit tests for the new function-chain builder types and SearchRequest integration/conflict validation.
src/include/milvus/types/FunctionChain.h	Introduces the public SDK types for function chains (stages, ops, expressions, args).
src/impl/types/FunctionChain.cpp	Implements the function-chain builder/types declared in the public header.
src/include/milvus/request/dql/SearchRequest.h	Adds function-chain API to SearchRequest and stores chains in the request object.
src/impl/request/dql/SearchRequest.cpp	Implements function-chain accessors/mutators and validates rerank vs. function-chains conflict.
src/impl/utils/TypeUtils.h	Declares ConvertFunctionChain() for proto serialization support.
src/impl/utils/TypeUtils.cpp	Implements function-chain proto serialization, including nested params/args encoding.
src/impl/MilvusClientV2Impl.cpp	Populates RPC function_chains on search requests.

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[codecov]

Codecov Report

❌ Patch coverage is 88.71795% with 22 lines in your changes missing coverage. Please review.
✅ Project coverage is 87.28%. Comparing base (a0592aa) to head (f4a1b8c).
⚠️ Report is 150 commits behind head on master.

Files with missing lines	Patch %	Lines
src/impl/types/FunctionChain.cpp	91.11%	8 Missing ⚠️
src/impl/utils/TypeUtils.cpp	86.66%	8 Missing ⚠️
src/impl/MilvusClientV2Impl.cpp	25.00%	3 Missing ⚠️
src/impl/request/dql/SearchRequest.cpp	92.50%	3 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff             @@
##           master     #586       +/-   ##
===========================================
+ Coverage   53.47%   87.28%   +33.80%     
===========================================
  Files          52      381      +329     
  Lines        4432    15991    +11559     
  Branches        0     1752     +1752     
===========================================
+ Hits         2370    13957    +11587     
+ Misses       2062     2034       -28     

Files with missing lines	Coverage Δ
src/include/milvus/request/dql/SearchRequest.h	100.00% <ø> (ø)
src/include/milvus/types/FunctionChain.h	100.00% <100.00%> (ø)
src/impl/MilvusClientV2Impl.cpp	80.04% <25.00%> (ø)
src/impl/request/dql/SearchRequest.cpp	92.98% <92.50%> (ø)
src/impl/types/FunctionChain.cpp	91.11% <91.11%> (ø)
src/impl/utils/TypeUtils.cpp	89.78% <86.66%> (ø)

... and 392 files with indirect coverage changes

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[mergify]

@yhmo Thanks for your contribution. Please submit with DCO, see the contributing guide https://github.com/milvus-io/milvus/blob/master/CONTRIBUTING.md#developer-certificate-of-origin-dco.