docs: add DR-002-strat for Eclipse project structure decision

docs/design_decisions/DR-002-strat.rst

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+..
+   Copyright (c) 2026 Contributors to the Eclipse Foundation
+
+   See the NOTICE file(s) distributed with this work for additional
+   information regarding copyright ownership.
+
+   This program and the accompanying materials are made available under the
+   terms of the Apache License Version 2.0 which is available at
+   https://www.apache.org/licenses/LICENSE-2.0
+
+   SPDX-License-Identifier: Apache-2.0
+
+DR-002-Strat: Eclipse Project Structure for S-Core
+===================================================
+
+- **Date:** 2026-05-22
+
+.. dec_rec:: Eclipse Project Structure for S-Core
+   :id: dec_rec__strat__eclipse_project_structure
+   :status: accepted
+   :context: Strategy
+   :decision: Option 1
+
+Context / Problem
+-----------------
+
+The strategic decision to treat S-Core as a platform rather than a collection of independent
+modules was already taken in DR-001-Strat. This decision record focuses solely on the technical
+question of how to structure the S-Core project within the Eclipse Foundation and GitHub.
+
+Two organisational models are under consideration: keeping all modules within one Eclipse project
+(the current approach), or splitting each module into a separate Eclipse project.
+
+The choice has implications for community governance, Committer nomination processes, GitHub
+organisation management, and the long-term risk to the S-Core v1.0 release.
+
+Options Considered
+------------------
+
+Option 1: One Eclipse Project (currently used)
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+All S-Core relevant modules reside together in one GitHub organisation under one Eclipse project.
+
+.. uml::
+   :align: center
+   :caption: Option 1 – One Eclipse project containing all S-Core repositories
+
+   skinparam componentStyle rectangle
+
+   component "eclipse" as ef <<Eclipse Foundation>> {
+      component "eclipse-score" as org <<GitHub Organisation>> {
+         component "score" as score
+         component "feo" as feo
+         component "baselibs" as baselibs
+         component "logging" as logging
+         component "persistence" as persistence
+         component "process_description" as proc
+         component "docs-as-code" as dac
+      }
+   }
+
+   score -[hidden]right- feo
+   feo -[hidden]right- baselibs
+   baselibs -[hidden]right- logging
+   score -[hidden]down- persistence
+   persistence -[hidden]right- proc
+   proc -[hidden]right- dac
+
+**Pros**
+
+- All S-Core relevant modules are together in one GitHub organisation → it is immediately visible
+  what belongs to the S-Core project.
+- One infrastructure, one timeline, one community → things are kept together.
+- One authority (PLs) for all modules that can ensure the same behaviour for all modules.
+
+**Cons**
+
+- Eclipse Foundation project handbook rules were not designed for such big projects. This leads
+  among others to the following problems:
+
+  - It is typically not possible to nominate initial Committers for newly contributed modules.
+  - The Committer model does not completely scale for such big projects. Having a large number of
+    modules in one Eclipse project leads to the necessity of having a big number of Committers
+    with various areas of responsibility.
+
+**Possible mitigation**
+
+- Eclipse Foundation and PMC must acknowledge and agree that new modules in S-Core are treated
+  as new Eclipse projects for the purpose of initial Committer nomination.
+- Mapping/restricting of Committer responsibilities in the project to dedicated areas is done
+  using the CODEOWNERS file in GitHub (already in place).
+
+Option 2: Multiple Eclipse Projects
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+Every module becomes its own Eclipse project; a central S-Core project serves as the integration
+project.
+
+.. uml::
+   :align: center
+   :caption: Option 2 – Multiple Eclipse projects, S-Core as the central integration project
+
+   top to bottom direction
+   skinparam componentStyle rectangle
+
+   component "eclipse (parent)" as ef_parent <<Eclipse Foundation>> {
+      component "eclipse-score / score\n(integration project)" as score_central
+   }
+
+   component "eclipse A" as ef_a <<Eclipse Foundation>> {
+      component "... / baselibs" as baselibs
+   }
+
+   component "eclipse B" as ef_b <<Eclipse Foundation>> {
+      component "... / logging" as logging
+   }
+
+   component "eclipse ..." as ef_n <<Eclipse Foundation>> {
+      component "..." as more
+   }
+
+   score_central <.. baselibs : sub-project
+   score_central <.. logging  : sub-project
+   score_central <.. more     : sub-project
+
+**Pros**
+
+- Every module is a "small" Eclipse project, which is exactly what the Eclipse Foundation project
+  handbook is built for → Clear Committer/Contributor/PL management.
+
+**Cons**
+
+- Every project is a completely standalone project. The S-Core project PLs do not have tools to
+  manage the separate Eclipse projects with implementation modules, which creates a significant
+  risk that the S-Core community could fracture.
+- Every module/project has its own GitHub Organisation → enforcing the same rules and processes
+  is complicated; belonging to S-Core project is not obvious.
+
+**Possible mitigation**
+
+- Currently no possible mitigations known for Cons 1.
+- The Eclipse Foundation technically enables S-Core and all sub-projects/modules to be located
+  within the same GitHub organisation.
+
+Conclusion
+----------
+
+**We proceed with Option 1**
+
+Rationale
+^^^^^^^^^
+
+- There are currently no major blockers that would make the switch to Option 2 obligatory.
+- Switching the structure of the project and module repositories poses a high risk for the
+  S-Core v1.0 release, which is planned for the end of the year.
+
+Follow-up Actions
+^^^^^^^^^^^^^^^^^
+
+- **X-Core approaches Eclipse Foundation**: Eclipse Foundation and PMC must acknowledge and agree
+  that new modules in S-Core are treated as new Eclipse projects for the purpose of initial
+  Committer nomination.