Fix mediatype for api json format

[mingan666]

Fix #1847

Changes mediatype to application/json

[plegall]

Hi @mingan666

Thank you for this pull-request. Why don't we immediately merge it, as it seems so obvious it's the right fix? Because we don't want to break third party applications which would rely on the current text/plain mediatype.

Related to #1107 #406 or #448

The question is for me : how to make things right with application/json but not break old third party apps relying on text/plain? Then you understand why it's not as easy as it seems :-/

[plegall]

(I closed this PR by mistake, sorry)

[mingan666]

Thanks for the explanation.

I understand your concern, but at the same time the current bug is causing problems for 3th party libraries that are not able to recognize the response as json.
Would it be possible to add an additional query parameter requesting the proper mediatype?

Not that good at php so I'm not sure how to implement such a solution...

[mingan666]

Quick look suggest it would be possible to add an additional format into include/ws_init.inc.php and tools/ws.htm.
As well as an additional class that could extend include/ws_protocols/json_encoder.php

Not the finast solution, but it gives users that want a correct mediatype that option, without breaking exiting integrations.
As I wrote above, not that good att php so I might be missing other parts that might need tweaking as well...