Fix config merger

[vjik]

Q	A
Is bugfix?	✔️
New feature?	❌
Breaks BC?	❌

Fix #153

[what-the-diff[bot]]

PR Summary

• Added new feature to handle duplication exceptions The change log has been updated to include a specific exception handling for situations involving 'Duplicate key' when using nested groups. This addition will effectively manage any duplication errors and improve overall functionality.

• Enhancement in Config.php Two new methods - shelve() and unshelve() have been added to Config.php. These methods, particularly useful for managing temporary storage spaces.

• Update in Merger.php A new storage property ($shelveStorage) has been added in the Merger.php file along with the same shelve() and unshelve() methods, further streamlining data management processes.

• New integrative tests and schemas To ensure that everything works perfectly, we've introduced a new test file (NestedGroupBug153Test.php) and setup files (di.php and di-web.php) in the tests/Integration/NestedGroupBug153 folder.

• Package management improvements A new composer.json file has been added in the tests/Integration/NestedGroupBug153/packages/a folder. With this, we now have better management and understanding of the project's dependencies.

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Comparison is base (8ef9884) 100.00% compared to head (d457d2d) 100.00%.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #163 +/- ## =========================================== Coverage 100.00% 100.00% Complexity 277 277 =========================================== Files 22 22 Lines 728 725 -3 =========================================== - Hits 728 725 -3 ```

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