Documentation for configuring the default aggregation temporality env var (#527)

Co-authored-by: Piotr Kiełkowicz <[email protected]>

Author: ysolomchenko

tools/MatrixHelper/SettingsData.cs

@@ -47,6 +47,7 @@ public static Setting[] GetSettings()
             new("OTEL_EXPORTER_OTLP_ENDPOINT", "The URL to where traces and metrics are sent. The default value is `http://localhost:4318`. Setting a value overrides the `SPLUNK_REALM` environment variable.", string.Empty, "string", ExporterCategory),
             new("SPLUNK_REALM", "The name of your organization's realm, for example, `us0`. When you set the realm, telemetry is sent directly to the ingest endpoint of Splunk Observability Cloud, bypassing the Splunk Distribution of OpenTelemetry Collector.", string.Empty, "string", ExporterCategory),
             new("SPLUNK_ACCESS_TOKEN", "A Splunk authentication token that lets exporters send data directly to Splunk Observability Cloud. Unset by default. Required if you need to send data to the Splunk Observability Cloud ingest endpoint.", string.Empty, "string", ExporterCategory),
+            new("OTEL_EXPORTER_OTLP_METRICS_TEMPORALITY_PREFERENCE", "The aggregation temporality to use on the basis of instrument kind. The supported options are: `Cumulative` (choose cumulative aggregation temporality for all instrument kinds.), `Delta` (choose Delta aggregation temporality for Counter, Asynchronous Counter and Histogram instrument kinds, choose Cumulative aggregation for UpDownCounter and Asynchronous UpDownCounter instrument kinds). `LowMemory`, known from OpenTelemetry specification is not supported.", "Cumulative", "string", ExporterCategory),
 
             // profiling
             new("SPLUNK_PROFILER_ENABLED", "Activates AlwaysOn Profiling.", "false", "boolean", ProfilingCategory),