Support DisallowUnknownFields in JSON

[ghost]

Currently it is not possible to tell the default JSON binder to use DisallowUnknownFields (supported by jsoniter and default Go json decoder). Use package variable EnableDecoderKnownFieldsOnly as a switch.

[tcr-ableton]

Why is this closed, I could really use this too 👍

[kszafran]

@tcr-ableton I would also find this feature useful. I created this PR: #2028

[codecov]

Codecov Report

Merging #1649 into master will decrease coverage by 0.24%.
The diff coverage is 100%.

@@            Coverage Diff             @@
##           master    #1649      +/-   ##
==========================================
- Coverage   99.28%   99.04%   -0.25%     
==========================================
  Files          40       43       +3     
  Lines        1971     2938     +967     
==========================================
+ Hits         1957     2910     +953     
- Misses         10       19       +9     
- Partials        4        9       +5

Impacted Files	Coverage Δ
binding/json.go	95.83% <100%> (-4.17%)	⬇️
render/json.go	95.37% <0%> (-4.63%)	⬇️
response_writer.go	96.72% <0%> (-3.28%)	⬇️
logger.go	98.7% <0%> (-1.3%)	⬇️
recovery.go	98.93% <0%> (-1.07%)	⬇️
context.go	99.27% <0%> (-0.23%)	⬇️
debug.go	95.65% <0%> (-0.1%)	⬇️
auth.go	100% <0%> (ø)	⬆️
binding/form.go	100% <0%> (ø)	⬆️
render/redirect.go	100% <0%> (ø)	⬆️
... and 11 more

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[ghost]

I've reopened the PR. It's possible to write your own binder and implement this behaviour that way however it seems like a nothing to add it here too.

[appleboy]

move to #2028