Primary changes:
* Strictly typed unmarshalling of metric values
* Schema types are contained by the processor (no "type entity002")
Minor changes:
* Added ProcessorFunc type for expressing processors as simple
functions.
* Added non-destructive `Merge` method to `model.LabelSet`
ProcessorForRequestHeader now looks first for a header like
`Content-Type: application/json; schema="prometheus/telemetry";
version="0.0.1"` before falling back to checking
`X-Prometheus-API-Version`.
We're currently timestamping samples with the time at the end of a scrape
iteration. It makes more sense to use a timestamp from the beginning of the
scrape for two reasons:
a) this time is more relevant to the scraped values than the time at the
end of the HTTP-GET + JSON decoding work.
b) it reduces sample timestamp jitter if we measure at the beginning, and
not at the completion of a scrape.
client_golang was updated to support full label-oriented telemetry,
which introduced interface incompatibilities with the previous
version of Prometheus. To alleviate this, a general fetching and
processing dispatching system has been created, which discriminates
and processes according to the version of input.
