feat: refactor SchemaModelService to update appMetadata when creating new data model

[standeren]

Description

Refactor SchemaModelService to update appMetadata when creating new data model:

• Remove some functions that was executed multiple times and instead only pass the calculated value that was actually needed in the underlying functions.
• Simplified UpdateCSharpClasses to only update csharp classes and move the logic to get the full type name out in separate method GetFullTypeName. Also created a separate function for NamespaceNeedsToBeSeparated that is now used in UpdateCSharpClasses.
• Removed return value of UpdateModelFilesFromJsonSchema as it was not used.
• Moved call to UpdateApplicationMetadata function from ProcessNewXsd to BuildSchemaFromXsd.
• Changed name of ProcessNewXsd to GenerateJsonSchemaAndCSharp since that is more concrete.
• The most crucial change is adding call to UpdateApplicationMetadata function in CreateSchemaFromTemplate.
• Deleted SerializeModelMetadata since it was not used.

In addition I changed the name of fileName in the BuildSchemaFromXsd, which is called when uploading xsd, to fileNameWithExtension to make a clearer what variables of the name that has extensions and not.

Related Issue(s)

• Ensure dataModelId is added to appMetadata on create new model #14123

Verification

• Your code builds clean without any errors or warnings
• Manual testing done (required)
• Relevant automated test added (if you find this hard, leave it and we'll help out)

[TomasEng]

Ingenting å utsette på dette så vidt jeg kan se. Fin og utfyllende beskrivelse!

[ErlingHauan]

Test OK 🚀

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 95.52%. Comparing base (37d92b5) to head (f7691ce).
Report is 2 commits behind head on main.

Additional details and impacted files

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##             main   #14209   +/-   ##
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  Coverage   95.52%   95.52%           
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  Files        1826     1826           
  Lines       23757    23757           
  Branches     2752     2752           
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  Hits        22695    22695           
  Misses        807      807           
  Partials      255      255           

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