Support 'default' rule for sequence and mapping.

[MrQubo]

Currently 'default' can only be used with scalar types. It should be possible to specify a default value for mappings and sequences too.

See this schema for example:

---
type: map
mapping:
  eggs:
    type: map
    mapping:
      foo:
        type: str
        required: true
      bar:
        type: int
        required: true
    default:
      foo: hello
      bar: 42

With this schema, empty root mapping should be valid and it would default too:

eggs:
  foo: hello
  bar: 42

But if the eggs key is present then both foo and bar must be specified, so this one shouldn't be valid with above schema:

eggs:
  foo: hello

[Grokzen]

Yes and no. I kinda get the idea, but i do not really like the syntax done like that. The solution should not be to just have a default value but a more flexible system where you can define 1-any number of possible validations for a given key, not just to have one main and one default.

[MrQubo]

@Grokzen Do you mean something like this?
Sounds like a good idea for me. But I cannot see how would it help with this issue.

[Grokzen]

Yes kinda like that. But i have not been implementing that kind of idea or many other ideas that i have since then i would just be reimplementing jsonschema and that is not the point of pykwalify.