* Document per-collection API metrics (v1.18.0)
Add a footnote to rest_responses_total and grpc_responses_total in the
metrics table and a new "Per-Collection API Metrics" subsection explaining
the ?per_collection=true query parameter added in qdrant/qdrant#8214.
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
* Consistently use title case
* Review feedback
* Edit
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Co-authored-by: Claude Sonnet 4.6 <noreply@anthropic.com>