feature: PRODUCT aggregation

[Seddryck]

• New aggregation in dictionary and as a C# class
• Review template for aggregations to handle missing elements in dictionary
• Create a specific template for PRODUCT for both Postgresql and Microsoft SQL Server

[codecov-commenter]

Codecov Report

Attention: 1 lines in your changes are missing coverage. Please review.

Comparison is base (8148050) 89.31% compared to head (04282f6) 89.42%.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #96 +/- ## ========================================== + Coverage 89.31% 89.42% +0.10% ========================================== Files 122 123 +1 Lines 1142 1144 +2 Branches 90 90 ========================================== + Hits 1020 1023 +3 + Misses 95 94 -1 Partials 27 27 ``` | [Files](https://app.codecov.io/gh/Seddryck/Tseesecake/pull/96?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=C%C3%A9dric+L.+Charlier) | Coverage Δ | | |---|---|---| | [...ling/Statements/Aggregations/ProductAggregation.cs](https://app.codecov.io/gh/Seddryck/Tseesecake/pull/96?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=C%C3%A9dric+L.+Charlier#diff-VHNlZXNlY2FrZS9Nb2RlbGluZy9TdGF0ZW1lbnRzL0FnZ3JlZ2F0aW9ucy9Qcm9kdWN0QWdncmVnYXRpb24uY3M=) | `50.00% <50.00%> (ø)` | | ... and [1 file with indirect coverage changes](https://app.codecov.io/gh/Seddryck/Tseesecake/pull/96/indirect-changes?src=pr&el=tree-more&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=C%C3%A9dric+L.+Charlier)

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