defaultValue purpose

Hi!
I think it would be helpful to explain whether/or not there be a long-term effect of the defaultValue parameter value. It's not clear if defaultValue argument will be used only when adding a column (to provide a value for existing rows only) or if the value will be written as a constraint (with a fixed value) to affect ALL future INSERTs. The documentation is lacking clarity, please explain. We have high hopes for this column (since defaultValueSql setting would be provider-specific, for instance a benign GETDATE() call will work in MS-SQL but fail against a Postgres database, where the function name is NOW()).

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* Content: [MigrationBuilder.AddColumn Method (Microsoft.EntityFrameworkCore.Migrations)](https://docs.microsoft.com/en-us/dotnet/api/microsoft.entityframeworkcore.migrations.migrationbuilder.addcolumn?f1url=https%3A%2F%2Fmsdn.microsoft.com%2Fquery%2Fdev16.query%3FappId%3DDev16IDEF1%26l%3DEN-US%26k%3Dk(Microsoft.EntityFrameworkCore.Migrations.MigrationBuilder.AddColumn%60%601);k(SolutionItemsProject);k(DevLang-csharp)%26rd%3Dtrue&view=efcore-3.1)
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