docs: add decision record about splitting the GradlePlugins repo (#3141)

docs/developer/decision-records/2023-06-02-separating_plugins_and_metamodel/README.md

@@ -0,0 +1,37 @@
+# Splitting up `GradlePlugins` repo
+
+## Decision
+
+The [GradlePlugins repository](https://github.com/eclipse-edc/GradlePlugins) currently contains the `runtime-metamodel`
+module, which will be moved out into a separate GitHub repository named `Runtime-Metamodel`.
+
+## Rationale
+
+This endeavour is meant to rectify the dependency graph, which currently contains a cyclic dependency between at least
+one of our Gradle plugins (`edc-build`) and the `runtime-metamodel` module.
+
+Moving out the `runtime-metamodel` module into a separate repository will not only break that cycle, it will also keep
+the `GradlePlugins` repo focused on what it was intended to contain: Gradle plugins.
+That in turn could come in handy, once the build process for plugins starts to deviate from our other components, i.e.
+publishing to the Gradle Portal instead of MavenCentral.
+
+## Approach
+
+- Open an EF HelpDesk ticket, requesting that additional repo
+- Move out the code
+- Update the release pipeline
+- Have all plugins use the `runtime-metamodel` artefact from Sonatype instead of a direct project dependency
+
+It must be noted that once this is done, the `runtime-metamodel` cannot leverage the `edc-build` plugin anymore, as that
+would
+obviously re-introduce the cycle. Rather, the relevant parts of the build configuration will be replicated there, most
+notably the publishing and signing configuration.
+
+## Further considerations
+
+Although it would probably be possible for the `runtime-metamodel` to use an older already published version of the
+build
+plugin, assuming the relevant parts of the build plugins publish configuration don't change very often, it seems to be a
+rather unelegant solution, because that would add a lot of unused dependencies and other spurious configuration to
+the `runtime-metamodel`. Further, it could theoretically introduce subtle bugs that stem from a version discrepancy of
+any one of the plugins.

docs/developer/decision-records/README.md

@@ -61,3 +61,4 @@
 - [2023-05-17-Helm-charts](2023-05-17-delete-helm-charts)
 - [2023-05-23-Java-17-baseline](2023-05-23-java-17-baseline)
 - [2023-05-25-template-repository](2023-05-25-template-repository)
+- [2023-06-02-separating_plugins_and_metamodel](2023-06-02-separating_plugins_and_metamodel)