Support `INCLUDE` for indexes (PG11)

[oguzhantopcu]

https://paquier.xyz/postgresql-2/postgres-11-covering-indexes/

Is there any way to add covering index via fluent mapping? If there is not, is it possible to implement?

[austindrenski]

I don't believe we've implemented any PG11 features yet, but we are certainly open to it.

Could you link to the official docs for the feature you're requesting, as well as provide some snippets (psuedo-code where necessary) of what you're envisioning?

[YohDeadfall]

It's a usual index with INCLUDEd columns (docs). The implementation could be taken from dotnet/efcore#12266 which was for SQL Server.

[austindrenski]

Ah, that makes sense. In that case we could probably put something together for this after #662.

[austindrenski]

@khellang Since you were just working in this area, would you be interested in submitting a PR?

[khellang]

Sure. I'll look into it tonight 👍🏻

[roji]

Merged, thanks @khellang!