Update release docs

Signed-off-by: Fabian Stäber <[email protected]>

MAINTAINER_NOTES.md

@@ -8,15 +8,60 @@ Use the [Versions Maven Plugin](https://www.mojohaus.org/versions-maven-plugin/i
 ./mvnw versions:use-latest-releases
 ```
 
+The versions plugin does not catch the `otel.version` in `prometheus-metrics-exporter-opentelemetry`. This needs to be updated manually.
+
+## Update Shaded Dependencies
+
+There are two modules for shaded dependencies:
+* `prometheus-metrics-shaded-opentelemetry`: OpenTelemetry data model.
+* `prometheus-metrics-shaded-protobuf`: Google's protobuf library.
+
+The shaded modules are commented out in the root `pom.xml`. Instead of using the shaded dependencies from the project, we use the latest shaded dependencies from Maven central (or from the local Maven repository in `~/.m2/repository/`). This way we can `include` the shaded package name directly. We find this easier than importing the original package name and have it renamed at build time.
+
+In order to update dependencies of the shaded modules (like Google's protobuf library or the OpenTelemetry library), do the following:
+
+Step 1: Install updated versions of the shaded dependencies in your local Maven repository.
+
+* Update the dependency versions in the shaded modules (both `*.version` and `*.version.string`).
+* `cd ./prometheus-metrics-shaded-dependencies ; ../mvnw install ; cd ..`
+
+Step 2: Update `prometheus-metrics-expositon-formats`
+
+* Change the version of the `prometheus-metrics-shaded-protobuf` dependency in `pom.xml` to `${project.version}`.
+* Update `PROTOBUF_VERSION_STRING` in `generate-protobuf.sh` and run the script to update the source code.
+* Use find-and-replace to update the version numbers in the imported package names in the source code of `prometheus-metrics-exposition-formats` and `prometheus-metrics-core`.
+
+Step 3: Update `prometheus-metrics-exporter-opentelemetry`
+
+* Change the version of the `prometheus-metrics-shaded-opentelemetry` dependency in `pom.xml` to `${project.version}`.
+* Use find-and-replace to update the version numbers in the imported package names in the source code of `prometheus-metrics-exporter-opentelemetry`.
+
+Step 4: Release
+
+_see below_
+
+Step 5:
+
+
 ## Release
 
+Create a commit to temporarily add shaded dependencies to the project:
+
+* Add the `prometheus-metrics-shaded-dependencies` module to the root `pom.xml`.
+* Change the versions of the shaded dependencies to `${project.version}` in `prometheus-metrics-exporter-opentelemetry` and `prometheus-metrics-exposition-formats`.
+
+Release:
+
 ```
 ./mvnw release:prepare -DreleaseVersion=1.2.0 -DdevelopmentVersion=1.3.0-SNAPSHOT
 ./mvnw release:perform -DreleaseVersion=1.2.0 -DdevelopmentVersion=1.3.0-SNAPSHOT
 ```
 
-`release:prepare` does Github tags and commits, while `release:perform` signs the artifacts and uploads them to the staging repositoring on [https://oss.sonatype.org](https://oss.sonatype.org).
+`release:prepare` does GitHub tags and commits, while `release:perform` signs the artifacts and uploads them to the staging repositoring on [https://oss.sonatype.org](https://oss.sonatype.org).
 
 After that, manually verify the uploaded artifacts on [https://oss.sonatype.org/#stagingRepositories](https://oss.sonatype.org/#stagingRepositories), click `Close` to trigger Sonatype's verification, and then `Release`.
 
-Note: We release only the parent module and the modules starting with simpleclient. Currently, we manually remove the benchmark and integration test modules. Todo: Instead of manually removing these modules, we should reconfigure the build to make sure that these modules aren't released.
+Create a commit to remove dependencies from the build (undoing the first step):
+
+* Comment out the `prometheus-metrics-shaded-dependencies` module to the root `pom.xml`.
+* Change the versions of the shaded dependencies to the latest released version on Maven Central in `prometheus-metrics-exporter-opentelemetry` and `prometheus-metrics-exposition-formats`.