JSON API: add support for login using JSON data

[sbesson]

Discovered while using the JSON API and failing to authenticate using curl --json. It took me a while to figure out this undocumented limitation especially since other JSON API POST endpoints expect the data to be sent as JSON.

The JSON API login endpoint delegates to the WebGateway LoginView logic which only support form data defined in the login form. This commit proposes to extend the LoginView.post() logic to also support authentication sent at JSON data.

There are a few ways to test this change:

• using curl --json with the appropriate headers
• using requests.post(login_url, json=payload) e.g. by modifying https://github.com/ome/openmicroscopy/blob/1ae1bfa5b831dc0225df48dbef7871cc6ab044f6/examples/Training/python/Json_Api/Login.py#L70 to use json rather than data

This change should not affect the ability to log in using the login page or the JSON API with form data.

[knabar]

I had not seen the len(request.POST) > 0 check before, but it should do what we want here. Code looks good to me.

[sbesson]

I had not seen the len(request.POST) > 0 check before, but it should do what we want here.

I found through debugging this was one of the ways to distinguish between a HTTPRequest form data and JSON data. I am still not 100% happy with this approach which looks fragile and I am considering using the value of request.content_type instead. Thoughts?

[will-moore]

If I try something invalid like:

r = session.post(login_url, json={'abc': 123})

I get a 500 html response (since I have DEBUG true) with local variable 'form' referenced before assignment at

        return self.handle_not_logged_in(request, error, form) 

[sbesson]

Thanks @will-moore, I hadn't tested the failing scenarios. After discussion with @knabar, pushed 42790d5 to 1- use the content type to detect JSON POST requests, 2- pass the JSON as a dictionary as an input to LoginForm. This significantly reduces the diff and means the login logic is largely unchanged and can use form.

ome/openmicroscopy#6420 should included updated integration tests for both valid and rejected JSON POST requests

[will-moore]

Working fine, thanks.
Tested successful login with data and json and invalid login with data and json. All with expected results.

[kkoz]

Works as expected