Draft for SQL Server identity fluent API in model snapshot

[roji]

@bricelam this is some quick draft work on #16922:

• Add new API to IAnnotationCodeGenerator to receive all annotations, allowing generating a single fluent API call for several annotations. Fully backwards-compatible.
• Implement handling for seed/increment via the new API
• Plumb IAnnotationCodeGenerator into CSharpSnapshotGenerator and use it to generate fluent API calls.
• Note: this currently removes annotations that are identified as by-convention by IAnnotationCodeGenerator from the context snapshopt - I'm guessing that's probably not good (since conventions may change across EF Core versions). If that's the case we should simply split IAnnotationCodeGenerator API - one for removing by-convention annotations, and another for generating fluent API calls.
• If we go down this route, we can just remove all the older IsHandledByConvention/GenerateFluentApi methods from the interface (but not from the base class), since we no longer call them directly.

If this looks like a good direction, let me know and I'll continue.

[AndriySvyryd]

Suggested change

	// First, handle built-in annotations
	// First, handle non-provider-specific annotations

[AndriySvyryd]

Note: this currently removes annotations that are identified as by-convention by IAnnotationCodeGenerator from the context snapshopt - I'm guessing that's probably not good (since conventions may change across EF Core versions). If that's the case we should simply split IAnnotationCodeGenerator API - one for removing by-convention annotations, and another for generating fluent API calls.

Yes, we should do this. Otherwise it's looking good (though more elaborate than I imagined it)

We should also consider using IAnnotationCodeGenerator to remove the annotations that are never generated - #15675

[bricelam]

+1 Looks good. Just need a way of generating by-convention annotations in the snapshot. Maybe a bool in HandleAnnotations()?

[roji]

@bricelam

Just need a way of generating by-convention annotations in the snapshot. Maybe a bool in HandleAnnotations()?

I actually thought of just exposing two APIs - one which removes annotations which are by convention (called when scaffolding but not when generating the snapshot), and one which removes annotations for which a fluent API exists (and returns the fluent API calls).

@AndriySvyryd

Otherwise it's looking good (though more elaborate than I imagined it)

Did I over-engineer? Any ideas for simplifying?

should also consider using IAnnotationCodeGenerator to remove the annotations that are never generated

Will do this too.

[AndriySvyryd]

Did I over-engineer? Any ideas for simplifying?

My initial design was just passing the string builder to the provider, but your way is better.

[roji]

Superceded by #21329