Added new business functions

[Gotnhub]

Summary

This PR introduces a new sink, business_rotating_sink, which routes log messages to different rotating log files based on a business tag/identifier. Each business has its own independent rotation state (max file size 30MB, max 3 rotated files kept). The implementation follows spdlog’s existing sink patterns (mt/st variants, header + -inl.h split), and includes unit tests integrated into the test build.

Motivation

In applications where multiple business modules share the same logging infrastructure, it’s often necessary to:

• write different business logs into different files
• keep separate rotation per business
• control disk usage (file size + number of historical files)
• select the target log file by passing a business tag when logging

Changes

Added

• include/spdlog/sinks/business_rotating_sink.h
  Declares business_rotating_sink and factory helpers.
• include/spdlog/sinks/business_rotating_sink-inl.h
  Inline implementation for template code (matches spdlog conventions).
• tests/test_business_rotating_sink.cpp
  New unit tests (8 test cases).

Modified

• src/file_sinks.cpp
  Adds template instantiations for business_rotating_sink (consistent with existing file sinks).
• tests/CMakeLists.txt
  Registers the new test source in the test target.
• tests/includes.h
  Adds the required include for the new sink header.

Implementation Notes

• Template-based design with business_rotating_sink_mt and business_rotating_sink_st, aligning with spdlog’s mt/st naming and threading model.
• One rotating_file_sink per business tag: each tag maps to its own rotating sink instance, maintaining independent file names and rotation state.
• Locking / deadlock avoidance: sink_it_ is implemented to avoid re-acquiring locks and prevents nested locking scenarios that could lead to deadlocks.
• Uses the standard *.h + *-inl.h split to keep template implementation in headers while preserving readability and build behavior.

Testing

• Business sink tests: 8 test cases / 32 assertions (tag: [business_rotating_sink])
• Full test suite: 189 test cases / 637 assertions — all passed

Notes

This is an additive feature and should not affect existing sinks or behavior.