resolve_string_connection

# File activerecord/lib/active_record/connection_adapters/abstract/connection_specification.rb, line 32
        def resolve_string_connection(spec) # :nodoc:
          hash = configurations.fetch(spec) do |k|
            connection_url_to_hash(k)
          end

          raise(AdapterNotSpecified, "#{spec} database is not configured") unless hash

          resolve_hash_connection hash
        end