Create default user when platform is created

[vinicvaz]

Create a default user with admin@email.com / admin credentials.
In the user creation we must install a list of default repositories in the user default workspace.
The list of repositories to be installed must be conditional to the existence of the platform github token, if no token provided we must install only the default_piece_repository to avoid exceding github request limit. If token provided we must install the following repositories:

• https://github.com/Tauffer-Consulting/default_pieces_repository
• https://github.com/Tauffer-Consulting/openai_domino_pieces
• https://github.com/Tauffer-Consulting/data_apis_domino_pieces
• others?

[luiztauffer]

@vinicvaz social media, because of youtube pieces, would be useful for starters