fix: do not try to create repository for abstract schema

[thiagomini]

Closes #131

[thiagomini]

Hey @B4nan , could you help me out with this PR? I'm trying to run yarn lint --fix in the project but it does not fix it. I believe this is using a different configuration.

This PR solves the issue I mentioned a while ago - the Nest module is trying to register repositories even for abstract schemas.

[B4nan]

Just remove the trailing space?

[B4nan]

I will close this, nowadays you can let the base entities be discovered automatically via references with EntitySchema too, just put the schema instance into the extends value. It's now done in all the examples in the docs this way.