Add additional-metadata option to interpolate action

[pgeier]

Description

To enable HEALPix interplation in the ClimateDT plans, the output metadata of the interpolate action should have a modified "resolution" key word. To allow overwriting/adding metadata, an additional option is required. This option is named "additional-metadata" and behaves similar to the option in the legacy encoder.

In previous versions this modification has been taken place in the legacy encode action.

Contributor Declaration

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• The code follows the project's coding standards.
• I have performed self-review and added comments where needed.
• I have added or updated tests to verify that my changes are effective and functional.
• I have run all existing tests and confirmed they pass.

🌈🌦️📖🚧 Documentation 🚧📖🌦️🌈
https://sites.ecmwf.int/docs/dev-section/multio/pull-requests/PR-259

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 56.28%. Comparing base (e133e49) to head (e1246bd).

Additional details and impacted files

@@             Coverage Diff             @@
##           develop     #259      +/-   ##
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+ Coverage    56.26%   56.28%   +0.01%     
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  Files          321      320       -1     
  Lines        21191    21198       +7     
  Branches      1686     1686              
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+ Hits         11924    11931       +7     
  Misses        9267     9267              

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[MircoValentiniECMWF]

I think that adding a passthrough mechanism to inject everything is not ok.
If we need to inject resolution we should add a n option to inject the resolution, or at least we should filter the "additionalMetadata"

[stefaniereuter]

@MircoValentiniECMWF I don't have a strong opinion either way. the additional metadata would be consistent with the approach that we have in the statistic mtg2 action and the way we have done it before:

new: https://git.ecmwf.int/users/ecm4053/repos/multio_plans/pull-requests/2/commits/bd164fb4be96ae592f6887d70d5bccf827b81b6c#climate-dt%2Fatmosphere%2F1_1_Hourly_HEALpix_high.yaml

old: https://git.ecmwf.int/projects/DE/repos/raps/browse/multio_yaml/multio-fesom.yaml?at=0.1.17#98

Is there a different reason, why you would like to add this additional protection layer? I'm okay to add the option resolution but I'm a bit worried that people think this would actually change something in the interpolate action and not just add metadata based on the before defined options.