docs (track/2): Update release notes for Otelcol v0.130 pin

docs/explanation/logging-architecture.md

@@ -249,8 +249,8 @@ The default retention period is 30 days. At the moment the loki charmed operator
 
 
 ## References
-- [Collect logs with Promtail](https://grafana.com/docs/grafana-cloud/send-data/logs/collect-logs-with-promtail/)
 - [Collect logs with opentelemetry-collector](https://grafana.com/docs/grafana-cloud/send-data/logs/collect-logs-with-otel/)
+- [Collect logs with Promtail](https://grafana.com/docs/enterprise-logs/latest/send-data/promtail/)
 - [Loki HTTP API][Push API]
 
 [Push API]: https://grafana.com/docs/loki/latest/reference/loki-http-api/

docs/explanation/telemetry-labels.md

@@ -113,7 +113,7 @@ all of the labels specified in the `stream` section above will be applied to all
 
 ## Scrape job labels for logs
 Log files can be scraped by Promtail or grafana agent, which then stream the log lines to Loki using Loki's `push-api` endpoint.
-Promtail, similar to grafana agent, has a [`scarpe_configs` section in its config file](https://grafana.com/docs/loki/latest/send-data/promtail/configuration/#scrape_configs) for specifying targets (log filename) and associate labels to them.
+Promtail, similar to grafana agent, has a [`scarpe_configs` section in its config file](https://grafana.com/docs/enterprise-logs/latest/send-data/promtail/) for specifying targets (log filename) and associate labels to them.
 See also grafana agent's [config file](https://grafana.com/docs/agent/latest/static/configuration/logs-config/) docs.
 
 

docs/reference/release-notes.md

@@ -26,6 +26,8 @@ COS 2 is compatible with Juju v3.6+. When deployed using terraform, Juju v3.6.11
 - `extra_alert_labels` config option. A new config option in grafana-agent and opentelemetry-collector enabled adding custom labels to alert rules. Custom labels are useful for differentiating alerts coming from sites with different SLAs.
 - **API links in catalogue-k8s**. The cards in catalogue-k8s now support extra links for documentation and APIs. COS charms now provide links to the workload API, making it easier to locate ingress URLs
 for workloads without a web UI.
+- **Opentelemetry collector**. Charmed opentelemetry-collector's workload is pinned to version 0.130 because the upstream `opentelemetry-collector-contrib` [project](https://github.com/open-telemetry/opentelemetry-collector-contrib) dropped support for Loki exporter in [release v0.131.0](https://github.com/open-telemetry/opentelemetry-collector-contrib/releases/tag/v0.131.0), stating that users can migrate to the OTLP exporters instead.
+  - The logging integrations for the `opentelemetry-collector` charms rely on `lokiexporter` to send logs to Loki push API endpoints. Loki only recently received upstream support for an OTLP endpoint, and migrating to an OTLP-first ecosystem in COS began in 26.04. The objective is to have support for OTLP ecosystem-wide by the end of 26.10 and to deprecate the Loki Push API feature (`logging` endpoint). Support will then be fully dropped in 27.04, and the `opentelemetry-collector` charms will no longer be pinned to `v0.130`.
 
 ## Notable changes in peripheral charms
 - Multiple scripts in script-exporter. The script exporter VM charm can now take an archive of scripts. It can now be deployed on 20.04, 22.04 and 24.04.