Fix for issue 975

[douglasbgray]

As stated in Issue 975, the reference resolver for properties does not fully recurse. This can lead to unresolved references when parsing with ParseOptions.setResolveFully(true) and there are properties with nested arrays/maps/composed schemas. The included test case has 10 variants of properties, of which 7 were not resolved fully before the change.

Prior to the fix, these are the failed test cases:

[ERROR] Failures: 
[ERROR]   OpenAPIV3ParserTest.testIssue975_allOf:1744 expected [#/components/schemas/Image] but found [./types.yaml#/components/schemas/Image]
[ERROR]   OpenAPIV3ParserTest.testIssue975_anyOf:1737 expected [#/components/schemas/Image] but found [./types.yaml#/components/schemas/Image]
[ERROR]   OpenAPIV3ParserTest.testIssue975_array_array:1715 expected [#/components/schemas/Image] but found [./types.yaml#/components/schemas/Image]
[ERROR]   OpenAPIV3ParserTest.testIssue975_array_map:1700 expected [#/components/schemas/Image] but found [./types.yaml#/components/schemas/Image]
[ERROR]   OpenAPIV3ParserTest.testIssue975_map_array:1707 expected [#/components/schemas/Image] but found [./types.yaml#/components/schemas/Image]
[ERROR]   OpenAPIV3ParserTest.testIssue975_map_map:1723 expected [#/components/schemas/Image] but found [./types.yaml#/components/schemas/Image]
[ERROR]   OpenAPIV3ParserTest.testIssue975_oneOf:1730 expected [#/components/schemas/Image] but found [./types.yaml#/components/schemas/Image]

One question - the tests are structured so that each Assert is in a separate test, to make it easy to see which properties were not parsed properly. If preferred, all tests can be merged into one test method, which is more compact. If so, I can close this PR and reissue with a PR in which the tests are replaced with this code:

    @Test(description = "Test that relative references are resolvable when property is a reference to a relative file.")
    @SuppressWarnings("unchecked")
    public void testIssue975() {
        ParseOptions options = new ParseOptions();
        options.setResolve(true);
        OpenAPI openAPI = new OpenAPIV3Parser().readLocation("issue-975/contract/openapi.yaml", null, options).getOpenAPI();

        assertEquals(2, openAPI.getComponents().getSchemas().size());
        assertTrue(openAPI.getComponents().getSchemas().containsKey("Image"));
        assertTrue(openAPI.getComponents().getSchemas().containsKey("MyResponse"));

        Schema myResponseSchema = openAPI.getComponents().getSchemas().get("MyResponse");
        Map<String, Schema> properties = myResponseSchema.getProperties();
        assertEquals(10, properties.size());

        assertEquals( properties.get("images").get$ref(), "#/components/schemas/Image");
        assertEquals( ((ArraySchema) properties.get("imagesArray")).getItems().get$ref(), "#/components/schemas/Image");
        assertEquals( ((Schema) properties.get("imagesMap").getAdditionalProperties()).get$ref(), "#/components/schemas/Image");
        assertEquals( ((Schema) ((ArraySchema) properties.get("imagesArrayMap")).getItems().getAdditionalProperties()).get$ref(), "#/components/schemas/Image");
        assertEquals( ((ArraySchema) properties.get("imagesMapArray").getAdditionalProperties()).getItems().get$ref(), "#/components/schemas/Image");
        assertEquals( ((ArraySchema) ((ArraySchema) properties.get("imagesArrayArray")).getItems()).getItems().get$ref(), "#/components/schemas/Image");
        assertEquals( ((Schema) ((Schema) properties.get("imagesMapMap").getAdditionalProperties()).getAdditionalProperties()).get$ref(), "#/components/schemas/Image");
        assertEquals( ((ComposedSchema) properties.get("oneOfExample")).getOneOf().get(0).get$ref(), "#/components/schemas/Image");
        assertEquals( ((ComposedSchema) properties.get("anyOfExample")).getAnyOf().get(0).get$ref(), "#/components/schemas/Image");
        assertEquals( ((ComposedSchema) properties.get("allOfExample")).getAllOf().get(0).get$ref(), "#/components/schemas/Image");
    }

[gracekarina]

thanks @douglasbgray