Fix APIv3 multi-parameter filter aggregation for range queries

[sergev-art]

Summary

Fixes a bug where APIv3 discarded all but the last filter parameter for a given field, breaking range queries like date$gt=X&date$lt=Y. Filter parameters are now properly aggregated into a compound MongoDB query.

• Root cause: parseFilter replaced the filter object for each parameter instead of merging
• Fix: Aggregates multiple filter operators for the same field into a single query object
• Tests: Adds verification tests for range queries and ISO8601 date filtering

Upstream: nightscout#8252

Design Control Impact

Modified Requirements

• API query specification (SR-level): Multi-parameter filtering on the same field shall aggregate operators, not replace them
• Date handling: APIv3 shall accept ISO8601 date strings in filter parameters

New Test Cases

• Range query: date$gt=X&date$lt=Y returns only entries within range
• ISO8601 date filter: date strings accepted and correctly parsed
• Single-field multi-operator: compound filters produce correct MongoDB query

Risk Items

• Data integrity: Incorrect filtering could return wrong glucose readings to clients/caregivers — incorrect treatment decisions could follow
• Silent failure: The bug produced no error — it simply returned a superset of requested data

Files Changed (2)

File	Change	Lines
lib/api3/storage/mongoCollection/utils.js	Fix filter aggregation logic	+19/-17
tests/api3.search.test.js	New range query and date tests	+77/-0