Fix: Migrate legacy name based roles

[abstraktor]

Changes

• fix(model-server): repository config roundtrips now
  • was broken for repos where the tree configuration of the first branch differs from the configuration of the master branch
  • now, it uses very same branch for validation and getting the config (the first one)
  • added regression test
• fix(model-datastructure): fix creating repositories with legacyNameBasedRoles=true for easier test setup (regression test included)
• refactor(model-server): allow calling RepositoriesManager.createEmptyTree from tests for easier test setup

[github-actions]

Test Results

131 files  131 suites   41m 7s ⏱️
741 tests 731 ✅ 9 💤 1 ❌
751 runs  741 ✅ 9 💤 1 ❌

For more details on these failures, see this check.

Results for commit d11c890.