Request to add a fluent entity existence check to entity creation and deletion statements

[TheSquidCombatant]

There is a fairly common scenario for applying updates to a database: create an entity if it does not exist, or delete an entity if it exists. Now the code looks like this:

    var exists = Schema
        .Table("Users")
        .Index("IX_Users_CreateDate")
        .Exists();

    if (!exists) Create
        .Index("IX_Users_CreateDate")
        .OnTable("Users")
        .OnColumn("CreateDate").Ascending();

But I would like to write the code like this:

    Create
        .Index("IX_Users_CreateDate")
        .OnTable("Users")
        .OnColumn("CreateDate").Ascending()
        .WithOptions().IfNotExists(); // no boilerplate code anymore

This would allow us not to write boilerplate code and avoid typos when duplicating the spelling of entity names.

[TheSquidCombatant]

Please check the implementation in this pull request #1801