Support additionalProperties in @OpenApiContent

[dzikoysk]

Requested on Javalin's Discord server

edit: example below

javalin-openapi/examples/javalin-gradle-kotlin/src/main/java/io/javalin/openapi/plugin/test/JavalinTest.java

Lines 145 to 158 in caf9a00

	@OpenApiContent( // map of simple types
	mimeType = "application/map-string-string",
	additionalProperties = @OpenApiAdditionalContent(
	from = String.class,
	exampleObjects = {
	@OpenApiExampleProperty(name = "en", value = "hey"),
	@OpenApiExampleProperty(name = "pl", value = "hejka tu lenka"),
	}
	)
	),
	@OpenApiContent( // map of complex types
	mimeType = "application/map-string-object",
	additionalProperties = @OpenApiAdditionalContent(from = Foo.class)
	),

[dzikoysk]

"application/map-string-object" : {
  "schema" : {
    "type" : "object",
    "additionalProperties" : {
      "$ref" : "#/components/schemas/Foo"
    }
  }
},
"application/map-string-string" : {
  "schema" : {
    "type" : "object",
    "additionalProperties" : {
      "type" : "string"
    }
  }
},

[dzikoysk]

Also added support for examples:

requestBody = @OpenApiRequestBody(
    description = "Supports multiple request bodies",
    content = {
        @OpenApiContent( // map of simple types
            mimeType = "application/map-string-string",
            additionalProperties = @OpenApiAdditionalContent(
                from = String.class,
                exampleObjects = {
                    @OpenApiExampleProperty(name = "en", value = "hey"),
                    @OpenApiExampleProperty(name = "pl", value = "hejka tu lenka"),
                }
            )
        ),
        @OpenApiContent( // map of complex types
            mimeType = "application/map-string-object",
            additionalProperties = @OpenApiAdditionalContent(from = Foo.class)
        ),

"application/map-string-object" : {
  "schema" : {
    "type" : "object",
    "additionalProperties" : {
      "$ref" : "#/components/schemas/Foo"
    }
  }
},
"application/map-string-string" : {
  "schema" : {
    "type" : "object",
    "additionalProperties" : {
      "type" : "string"
    },
    "example" : {
      "en" : "hey",
      "pl" : "hejka tu lenka"
    }
  }
},