Factor authorize_push! and authorize_code_access!

with existing `method_missing` in the same controller.

The pattern of leaving standard named methods like `authorize_` to `method_missing` is already used extensively, so let's be consistent and use it everywhere.

    git ls-files | xargs perl -lapi -e 's/authorize_code_access!/authorize_download_code!/g'
    git ls-files | xargs perl -lapi -e 's/authorize_push!/authorize_push_code!/g'