/metrics and errors response need a valid content-type header (application/json for example)

[lavcraft]

Use application/json instead of text/plain or use Accept header for generate expecting response

http :5050/metrics
HTTP/1.1 200 OK
content-encoding: gzip
content-type: text/plain;charset=UTF-8
transfer-encoding: chunked

{
    "classes": 8547,
    "classes.loaded": 8547,
    "classes.unloaded": 0,
    "gc.ps_marksweep.count": 2,
    "gc.ps_marksweep.time": 434,
    "gc.ps_scavenge.count": 15,
    "gc.ps_scavenge.time": 171,
    "heap": 455168,
    "heap.committed": 201728,
    "heap.init": 32768,
    "heap.used": 111608,
    "instance.uptime": 99692,
    "mem": 265370,
    "mem.free": 90119,
    "nonheap": 0,
    "nonheap.committed": 66576,
    "nonheap.init": 2496,
    "nonheap.used": 63644,
    "processors": 4,
    "systemload.average": 0.4912109375,
    "threads": 17,
    "threads.daemon": 7,
    "threads.peak": 17,
    "threads.totalStarted": 27,
    "uptime": 120674
}