fix: Do not expose debug in a response when a schema is not found

[sawadashota]

Related issue(s)

Do not expose debug in a response when a schema is not found.
This debug property does not look valuable for clients and just risks which is exposing server information such as middleware.

$  curl http://localhost:4455/.ory/kratos/public/schemas/not_found
{"error":{"code":404,"status":"Not Found","debug":"id=\nrid=\nerror=The request was malformed or contained invalid parameters\nreason=Unable to find JSON Schema ID: not_found\ndetails=map[]\ndebug=\n\ngit.luolix.top/ory/kratos/schema.Schemas.GetByID\n\t/project/schema/schema.go:37\ngit.luolix.top/ory/kratos/schema.(*Handler).getByID\n\t/project/schema/handler.go:106\ngit.luolix.top/ory/kratos/x.NoCacheHandle.func1\n\t/project/x/nocache.go:18\ngit.luolix.top/ory/kratos/x.NoCacheHandle.func1\n\t/project/x/nocache.go:18\ngit.luolix.top/julienschmidt/httprouter.(*Router).ServeHTTP\n\t/go/pkg/mod/github.com/julienschmidt/httprouter@v1.3.0/router.go:387\ngit.luolix.top/ory/nosurf.(*CSRFHandler).handleSuccess\n\t/go/pkg/mod/github.com/ory/nosurf@v1.2.7/handler.go:234\ngit.luolix.top/ory/nosurf.(*CSRFHandler).ServeHTTP\n\t/go/pkg/mod/github.com/ory/nosurf@v1.2.7/handler.go:185\ngit.luolix.top/urfave/negroni.Wrap.func1\n\t/go/pkg/mod/github.com/urfave/negroni@v1.0.0/negroni.go:46\ngit.luolix.top/urfave/negroni.HandlerFunc.ServeHTTP\n\t/go/pkg/mod/github.com/urfave/negroni@v1.0.0/negroni.go:29\ngit.luolix.top/urfave/negroni.middleware.ServeHTTP\n\t/go/pkg/mod/github.com/urfave/negroni@v1.0.0/negroni.go:38\ngit.luolix.top/ory/kratos/x.glob..func1\n\t/project/x/clean_url.go:12\ngit.luolix.top/urfave/negroni.HandlerFunc.ServeHTTP\n\t/go/pkg/mod/github.com/urfave/negroni@v1.0.0/negroni.go:29\ngit.luolix.top/urfave/negroni.middleware.ServeHTTP\n\t/go/pkg/mod/github.com/urfave/negroni@v1.0.0/negroni.go:38\nnet/http.HandlerFunc.ServeHTTP\n\t/usr/local/go/src/net/http/server.go:2047\ngit.luolix.top/prometheus/client_golang/prometheus/promhttp.InstrumentHandlerResponseSize.func1\n\t/go/pkg/mod/github.com/prometheus/client_golang@v1.11.0/prometheus/promhttp/instrument_server.go:198\nnet/http.HandlerFunc.ServeHTTP\n\t/usr/local/go/src/net/http/server.go:2047\ngit.luolix.top/prometheus/client_golang/prometheus/promhttp.InstrumentHandlerCounter.func1\n\t/go/pkg/mod/github.com/prometheus/client_golang@v1.11.0/prometheus/promhttp/instrument_server.go:101\nnet/http.HandlerFunc.ServeHTTP\n\t/usr/local/go/src/net/http/server.go:2047\ngit.luolix.top/prometheus/client_golang/prometheus/promhttp.InstrumentHandlerDuration.func1\n\t/go/pkg/mod/github.com/prometheus/client_golang@v1.11.0/prometheus/promhttp/instrument_server.go:68\nnet/http.HandlerFunc.ServeHTTP\n\t/usr/local/go/src/net/http/server.go:2047\ngit.luolix.top/prometheus/client_golang/prometheus/promhttp.InstrumentHandlerDuration.func2\n\t/go/pkg/mod/github.com/prometheus/client_golang@v1.11.0/prometheus/promhttp/instrument_server.go:76\nnet/http.HandlerFunc.ServeHTTP\n\t/usr/local/go/src/net/http/server.go:2047\ngit.luolix.top/prometheus/client_golang/prometheus/promhttp.InstrumentHandlerRequestSize.func1\n\t/go/pkg/mod/github.com/prometheus/client_golang@v1.11.0/prometheus/promhttp/instrument_server.go:165\nnet/http.HandlerFunc.ServeHTTP\n\t/usr/local/go/src/net/http/server.go:2047\ngit.luolix.top/ory/x/prometheusx.Metrics.instrumentHandlerStatusBucket.func1\n\t/go/pkg/mod/github.com/ory/x@v0.0.358/prometheusx/metrics.go:108\nnet/http.HandlerFunc.ServeHTTP\n\t/usr/local/go/src/net/http/server.go:2047\ngit.luolix.top/ory/x/prometheusx.(*MetricsManager).ServeHTTP\n\t/go/pkg/mod/github.com/ory/x@v0.0.358/prometheusx/middleware.go:30\ngit.luolix.top/urfave/negroni.middleware.ServeHTTP\n\t/go/pkg/mod/github.com/urfave/negroni@v1.0.0/negroni.go:38\ngit.luolix.top/ory/x/tracing.(*Tracer).ServeHTTP\n\t/go/pkg/mod/github.com/ory/x@v0.0.358/tracing/middleware.go:36\ngit.luolix.top/urfave/negroni.middleware.ServeHTTP\n\t/go/pkg/mod/github.com/urfave/negroni@v1.0.0/negroni.go:38\ngit.luolix.top/ory/x/metricsx.(*Service).ServeHTTP\n\t/go/pkg/mod/github.com/ory/x@v0.0.358/metricsx/middleware.go:275\ngit.luolix.top/urfave/negroni.middleware.ServeHTTP\n\t/go/pkg/mod/github.com/urfave/negroni@v1.0.0/negroni.go:38","message":"The requested resource could not be found"}}

Checklist

• I have read the contributing guidelines.
• I have referenced an issue containing the design document if my change
  introduces a new feature.
• I am following the
  contributing code guidelines.
• I have read the security policy.
• I confirm that this pull request does not address a security
  vulnerability. If this pull request addresses a security. vulnerability, I
  confirm that I got green light (please contact
  security@ory.sh) from the maintainers to push
  the changes.
• I have added tests that prove my fix is effective or that my feature
  works.
• I have added or changed the documentation.

[codecov]

Codecov Report

Merging #2348 (6a76e95) into master (bf970f3) will increase coverage by 0.00%.
The diff coverage is 100.00%.

❗ Current head 6a76e95 differs from pull request most recent head e1fec05. Consider uploading reports for the commit e1fec05 to get more accurate results

@@           Coverage Diff           @@
##           master    #2348   +/-   ##
=======================================
  Coverage   76.55%   76.55%           
=======================================
  Files         318      318           
  Lines       17298    17294    -4     
=======================================
- Hits        13242    13240    -2     
+ Misses       3122     3120    -2     
  Partials      934      934           

Impacted Files	Coverage Δ
schema/handler.go	82.27% <100.00%> (ø)
courier/courier.go	76.92% <0.00%> (+3.58%)	⬆️

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