Catches decode/processing failures in sensor ingest

[devleo10]

Summary

• Fixes Fail nicely when failing to decode measurements #498 by handling sensor measurement decode/processing failures gracefully and returning 400 instead of bubbling unhandled exceptions as 500.
• Hardens sensor endpoints to return explicit 400 for unsupported Content-Type values (instead of raising ValueError).
• Adds regression tests for malformed binary, garbage payloads, empty payload, and unsupported content-type paths to prevent future regressions.

What Changed

• backend/api/resources/util.py

  • Wrapped decode_measurement(...) in guarded error handling.
  • Wrapped process_measurement_dict(...) path to prevent unhandled exceptions from reaching Flask.
  • Added structured logging for failure paths.
  • Fixed co2 branch to append Photoresistivity insertion result consistently.
  • Added explicit unsupported-measurement fallback response (501) for unknown measurement types.

• backend/api/resources/sensor_data.py

  • Replaced error-raising content-type branch with explicit 400 response.
  • Uses request.mimetype so application/json; charset=utf-8 is handled correctly.

• backend/api/resources/sensor_data_json.py

  • Same content-type hardening as binary endpoint (400 instead of exception path).
  • Uses request.mimetype for robust content-type matching.

• backend/tests/test_sensor.py

  • Added tests:
    • invalid binary returns 400
    • garbage ascii payload returns 400
    • empty body returns 400
    • unsupported content type on /api/sensor/ returns 400
    • unsupported content type on /api/sensor_json/ returns 400

Why

Issue #498 showed decode failures surfacing as unhandled exceptions in production logs (/api/sensor/), causing internal server errors.
This PR ensures malformed client payloads are treated as client errors (400) with clear response messaging and test coverage.

Validation

• Manual check:
  • POST /api/sensor/ with invalid octet-stream payload now returns 400 with decode/processing error message.
• Automated tests:
  • tests/test_sensor.py passes with new regression scenarios covering the Fail nicely when failing to decode measurements #498 failure modes.

Risk / Impact

• Low risk: changes are localized to sensor request handling and tests.
• Behavior change is intentional and aligns with API expectations:
  • malformed requests → 400
  • unknown measurement type → 501
• No new third-party dependencies introduced.

[codecov]

Codecov Report

❌ Patch coverage is 61.03896% with 30 lines in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
backend/api/resources/util.py	35.89%	25 Missing ⚠️
backend/api/resources/sensor_data_json.py	58.33%	5 Missing ⚠️

Flag	Coverage Δ
backend	71.14% <61.03%> (+0.53%)	⬆️
frontend	52.18% <ø> (ø)

Flags with carried forward coverage won't be shown. Click here to find out more.

Files with missing lines	Coverage Δ
backend/api/resources/sensor_data.py	57.40% <100.00%> (+30.99%)	⬆️
backend/tests/test_sensor.py	100.00% <100.00%> (ø)
backend/api/resources/sensor_data_json.py	57.57% <58.33%> (+19.64%)	⬆️
backend/api/resources/util.py	49.04% <35.89%> (-3.72%)	⬇️

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[devleo10]

Before the fix

After the fix

[devleo10]

@jmadden173 @aleclevy Lemme know if this looks good.