add support for unique constraint

[SingingBush]

The @Column definition currently:

struct Column {
    immutable string name;
    immutable int length;
}

It would be great if there was a third parameter to mark a column as being unique:

struct Column {
    immutable string name;
    immutable int length;
    immutable bool unique;
}

[buggins]

I believe @UniqueKey() annotation is to be used instead
@entity
class Value {
@id @generated
int id;
@column("name") @UniqueKey("name_index")
string name;
}

Let me know if it's not working as expected.
Closing issue so far.

[SingingBush]

thanks for this. I've tried using it but it doesn't seem to work for me.

[KrzaQ]

I tried using it, it didn't work for me either.