Feature/adding shows backend

@s1mplex  - still have problems with 2 tests, please run them and fix them or tell me how to fix them:
shows_controller_spec.rb -> oba w describe "#create" -> 

RSpec::Mocks::MockExpectationError: Screen(id: integer, name: string, created_at: datetime, updated_at: datetime, cinema_id: integer) (class).find(any args)
    expected: 1 time with any arguments
    received: 0 times with any arguments