Added correct typing for has one create mixin values.

[Ranguna]

Hello everyone! I'm trying to make a wrapper around sequelize mixins and I stumbled upon this. If I understood the mixing correctly, the createModel mixin for hasOne association does not seem to have the correct typing for the creation values (accessible from Model["_creationAttributes"]).

Do these changes make sense ?

If yes, I can replicate them to all other association types.

[Ranguna]

Also, I just realized that I have a typo in the commit message, I can redo the commit if necessary.