[#211] Generate OpenAPI dictionaries without fixed keys as maps

[natsukagami]

Closes #211.

Generate all objects with the additionalProperties value set, but no properties set as maps.

For example, these schemas:

anyMap:
    type: object
    additionalProperties: true
numberMap:
    type: object
    additionalProperties:
        type: integer
mapWithFixedKeys:
    type: object
    additionalProperties:
        type: string
    properties:
        key:
            type: string

produces the following

type AnyMap map[string]interface{}

type NumberMap map[string]int

type MapWithFixedKeys struct {
    Key                  string
    AdditionalProperties map[string]string
}

instead of

type AnyMap struct {
    AdditionalProperties map[string]interface{}
}

type NumberMap struct {
    AdditionalProperties map[string]int
}

type MapWithFixedKeys struct {
    Key                  string
    AdditionalProperties map[string]string
}

This is a small breaking change.

[deepmap-marcinr]

Sorry to take so long to get to this.

Would you mind adding a configuration option for old schema behavior in the new Configuration struct, and allow disabling this new behavior? I guess we could call it "DisableFlattenAdditionalProperties" or something liek that - so that your new behavior is the default, but we can override it off. I'd be happy to merge this.

[deepmap-marcinr]

If not, I can take care of it, but I'm not entirely sure how to do it in github so you get a commit credit :)

[natsukagami]

Please take care of it. It's been a long time since I touched the codebase, I am no longer familiar with it.

As for the commit credit, I think as long as you merge or squash with the "Co-author" fields in the commit message intact GitHub will treat it well :P