Make a better distinction foreign key fulfillment and automatically adding inserts

[carl-berg]

Background

Currently this setting is controlled via Dude.EnableAutomaticForeignKeys(...), however quite a few users have misunderstood what the options here means. There are two concepts at play here:

1. Using previous inserts to set FK columns when inserting rows. The default behavior here is to always fill a dependency if it is available and the column value has not been set manually (to null for example). This is enabled by setting Dude.EnableAutomaticForeignKeys() with no parameters.

2. Analysing FK dependencies of tables being inserted to and automatically adding extra inserts where needed, depending on dependency traversal strategy. This is enabled by setting Dude.EnableAutomaticForeignKeys(c => c.AddMissingForeignKeys = true). It's also possible to set a dependency traversal strategy like this to change from the default strategy or plugging in your own strategy:

Dude.EnableAutomaticForeignKeys(c =>
{ 
    c.AddMissingForeignKeys = true;
    c.DependencyTraversalStrategy = DependencyTraversalStrategy.SkipNullableForeignKeys;
}

The problem

The confusion however seem to be that the dependency traversal strategy affects whether foreign keys are filled in scenario 1, which is not what it is for. I think this is a failure of the library api, it's not clear enough what the difference is and i think it could be changed to make the distinction clearer.

[carl-berg]

It could be a nice feature for a user to configure if they want automatic nullable FK inserts or not (both on a global scope and for an individual run)