Add CORS headers to gateway responses

[nick]

This allows JSON content served from the gateway to be consumed without a CORS error.

I just tried upgrading from 0.34 to 0.36 and found this issue... adding this extra config seemed to fix it.

[alanshaw]

Any chance we can get a test for this @nick so that it doesn't happen again?

[nick]

@alanshaw I tried adding a check for the headers in test/gateway/index.js but it seems 'access-control-origin' is not set in that context. Searching the test folder for 'cors' or 'access-control' didn't yield anything useful... do you have any pointers on where I could add an appropriate test?

[alanshaw]

test/gateway looks like the right place to add it - I guess you need to add a test that sends an OPTIONS request so the server sends a response back with CORS headers?

[nick]

Turns out CORS headers are only sent in the response if I set the 'Origin' header in the request. Have now added an appropriate test.

[alanshaw]

Perfect, thanks @nick!