Custom File Processor script associated with selected Data Maps should be automatically included (similar to Lookups).
If Custom Row Processors exist, an additional step in the wizard will be shown after selecting Data Maps called to provide an optional selection of Custom Row Processors.
Custom File Generators are not supported in templates.
No UI changes are required for importing templates.

Database Changes

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Table Change Justification
Preprocessors
New Table:
Id (PK, int)
Name (nvarchar(255) not null)
PreprocessorType (nvarchar(20), not null)
ScriptContent (nvarchar(max) null)
RequiresOdsApi (bit, not null)
Supports storage of PowerShell scripts.
EF Core note: Implement PreprocessorType as an enum.
DataMaps
New column:
FileProcessorId (FK, int, null)
Optionally associate a data map with a Custom File Processor.
Agents
Removed columns:
RowProcessor (nvarchar(max), null)
FileGenerator (nvarchar(max), null)
New columns:
RowProcessorId (FK, int, null)
FileGeneratorId (FK, int, null)
Replace Custom Row Processor and Custom File Generator filenames with database references.
This will require a specialized migration:
Create a preprocessor record with Name of the current value.
Reference it from the new column, and drop the old column.
On web application startup, for any Preprocessor records with a null ScriptContent value, get the file from the file system (by Name and known path per PreprocessorType) and populate contents into Script Content.
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