Support xml representation of schema

[lgaida]

See #122

[coveralls]

Coverage increased (+0.05%) to 92.062% when pulling fc31b92 on lgaida:master into 519bcf6 on ePages-de:master.

[mduesterhoeft]

@lgaida thanks for your contribution.
I have to admit that I shy away a little bit from adding xml support. We never were in need for this feature and I have not much knowledge how spring-restdocs and openapi support xml. So I would rather not add this feature. @ozscheyge what do you think?

[ozscheyge]

Yep, indeed we didn't consider XML capabilities included in Spring restdocs/OpenAPI standards, but focused on our use-case which is HTTP+JSON.

Iirc, we have a couple of assumptions built on jsonpaths in the code.
Having had a brief look on the openapi3 part @lgaida linked, we would need way to populate the xml object with information.

Mapping jsonpath to xpath might seem like a quick win, but first it's error-prone (couldn't find a library ad-hoc) and second you'd still lose information.

[lgaida]

Thanks for your replies :)
It is totally understandable that you created this tool with your own use-cases in mind.
 In fact i’m thankful that you are sharing this tool as an open-source project. Http+Json is the most common use-case, so you’re already helping a lot of people out with this.



I just wanted to start a discussion here not leaving possibilities out since I see how xml support could enhance this tool.
 But as previously pointed out, a clean solution to this problem requires a lot of work. 
I may dig a little bit deeper into the whole xpath/jsonpath topic to verify whether it is actually possible to do a clean conversion between the two without information loss.

For now I’m totally fine with closing this PR and the issue itself.
 How about adding a notice to the REAME and explicitly point out that xml is currently not and most likely will never be supported ?