[engine] MuranoPL default for composite field is not working properly

[Alexander Tivelkov]

In the following example:

networks:
    Contract:
      environment: $.bool().notNull()
      flat: $.bool().notNull()
      custom: [$.class(Network).notNull()]
    Default:
      environment: true
      flat: false

field 'networks' is defined as map-like data structure with contracts on each field and the default for the whole object.
This does not work properly: the defaults are not properly constructed, and the contracts are not matched.

[Andrew Pashkin (apashkin)]

What if drop composite arguments and replace this feature with custom classes? It will be more simple.

[Stan Lagun (slagun)]

There is a per-field workaround that is already used in Environment class:
Contract:
  $.string() or 'test'

So lets leave Default as it is now so that 2 methods will behave differently to address different use cases and not to create duplication