mode=readwrite key/value pair gets skipped in the output of /gov/service/javascript-app?case=original

[gaurav137]

@eddyashton I tried the 6.0 dev11 release and picked up the ?case=original change per #6712 and seeing the following behavior.

If I specify case=original then if the app.json contains "mode": "readwrite" for any of the endpoints then the output of /gov/service/javascript-app?case=original is not reporting the mode key itself. Perhaps something to do with the default enum value not getting serialized? So this breaks our validation when comparing the proposed bundle with the output of this API.

I've worked around this by adding the missing mode key on our (client side) end if no mode key is reported in the API output. But filing the issue as it seems like an unintended behavior of the API and worth a discussion. Attempting to submit a bundle w/o a mode value fails so I think at the minimum the default enum value should also get serialized and saved? Hence it should not get skipped when reporting out the EndpointProperties as-is when case=original is specified.