Retrieve Metasys trend data, choosing correctly between the repository and the object buffer

Documented steps

1. Decide the source. The repository (/timeSeries/...) holds samples routed to the Site Director's historical store; the object buffer (/objects/{objectId}/trendedAttributes/...) holds samples still resident in the trend or log object itself. They answer different questions.
2. Discover trended objects with GET {base}/timeSeries?searchString={substringOfItemReference}&page=1&pageSize=100 (pageSize 1-2000; sort itemReference or -itemReference). Each item carries id, itemReference, name and sampledAttributes[] with a ready-made samplesUrl.
3. Pull repository samples with GET {base}/timeSeries/{objectId}/trendedAttributes/{attributeId}/samples?startSampleTime=...&endSampleTime=...&page=1&pageSize=500. pageSize defaults to 500 and maxes at 20000; sort defaults to -sampleTime.
4. Parse the response: {total, schema, items:[{value, sampleTime, reliability}], previous, next, self, timeSeriesUrl, attribute}. value is a number, boolean or string depending on the point.
5. Discard or flag any sample whose reliability is reliabilityEnumSet.unreliable - it indicates the BACnet fault status flag was set at sample time.
6. Pull buffer samples with GET {base}/objects/{objectId}/trendedAttributes/{attributeId}/samples?startSampleTime=...&endSampleTime=...&sampledById=... . This variant has no page or pageSize parameters.
7. Fetch many series in one call with POST {base}/timeSeries/batch and body {"method":"GET","requests":[{"id":"1","relativeUrl":"{objectId}/trendedAttributes/presentValue/samples?startSampleTime=...&endSampleTime=..."}]}. relativeUrl is relative to /timeSeries.
8. Follow 'next' to page rather than incrementing page numbers past 'total'.
9. Reference: https://jci-metasys.github.io/api-landing/api/v6-16 (Metasys REST API, 'Version 6 for 16.0', OpenAPI 3.0.3). Doc set index: https://jci-metasys.github.io/api-landing/ | changelog: https://jci-metasys.github.io/api-landing/guides/api-changelog/ | version support: https://jci-metasys.github.io/api-landing/guides/version-support-matrix/ | polling and streaming limits: https://jci-metasys.github.io/api-landing/guides/attribute-access-guidelines/