[Enh]: For auto-config entities support `@file()`

[JerryNixon]

What

Allow autoentities.template to reference external metadata files using the new @file() syntax.

This enhancement allows auto-generated entities to inherit descriptions or other metadata from configuration-managed metadata files.

This enhancement depends on the following:

• [Enh]: Support autoentities #2794
• [Enh]: Support @file() substitution function. #2863

New properties

This uses the new @file() syntax but behaves differently from normal configuration replacements. Because internal macros such as {schema}, {object}, {column}, and {parameter} are resolved dynamically within the auto-entity generation loop, these replacements cannot occur during configuration load. Instead, they must be evaluated after auto-generated entities have been expanded.

{
  "template": {
    "description": "@file('{schema}.{object}.MS_Description')", // table-level
    "source": {
      "parameters": {
        "description": "@file('{schema}.{object}.@{parameter}.MS_Description')" // parameter-level
      }
    },
    "fields": {
      "description": "@file('{schema}.{object}.{column}.MS_Description')" // column-level
    }
  }
}

In this case the metadata keys correspond to entries in the metadata files configured through metadata-files.

Example metadata file:

{
  "dbo.Author.MS_Description": "Author records in the system",
  "dbo.Author.Id.MS_Description": "Primary key of the author",
  "dbo.GetCustomer.@CustomerId.MS_Description": "Identifier of the requested customer"
}

During auto-entity generation, the template macros are expanded first and the resulting keys are resolved using @file() against the merged metadata dictionary.