docs: Explanation - pin workloads to 0.130 (#220)

Author: MichaelThamm

docs/.custom_wordlist.txt

@@ -21,6 +21,7 @@ CMRs
 config
 configs
 contextualize
+contrib
 cpu
 cryptographic
 cryptographically

docs/reference/release-notes.md

@@ -31,6 +31,8 @@ COS 3 is compatible with Juju v3.6+.
 
 ## What's new in COS 3
 
+- **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`.
 
 ### COS components
 
@@ -51,9 +53,6 @@ COS 3 is compatible with Juju v3.6+.
 ### COS Lite components
 
 
-
-
-
 ## Notable changes in peripheral charms