[8.x](backport #40997) x-pack/filebeat/input/internal/private: add field redaction package

[mergify]

Proposed commit message

Initial donation of code from github.com/kortschak/dex/internal/private.

Checklist

• My code follows the style guidelines of this project
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• I have made corresponding change to the default configuration files
• I have added tests that prove my fix is effective or that my feature works
• I have added an entry in CHANGELOG.next.asciidoc or CHANGELOG-developer.next.asciidoc.

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How to test this PR locally

Related issues

Use cases

diff --git a/x-pack/filebeat/input/httpjson/input.go b/x-pack/filebeat/input/httpjson/input.go
index 67daa7ef84..41b46c1878 100644
--- a/x-pack/filebeat/input/httpjson/input.go
+++ b/x-pack/filebeat/input/httpjson/input.go
@@ -33,6 +33,7 @@ import (
        "github.com/elastic/beats/v7/libbeat/version"
        "github.com/elastic/beats/v7/x-pack/filebeat/input/internal/httplog"
        "github.com/elastic/beats/v7/x-pack/filebeat/input/internal/httpmon"
+       "github.com/elastic/beats/v7/x-pack/filebeat/input/internal/private"
        "github.com/elastic/elastic-agent-libs/logp"
        "github.com/elastic/elastic-agent-libs/mapstr"
        "github.com/elastic/elastic-agent-libs/monitoring"
@@ -82,6 +83,19 @@ func (log *retryLogger) Warn(msg string, keysAndValues ...interface{}) {
        log.log.Warnw(msg, keysAndValues...)
 }
 
+type redact struct {
+       value  mapstr.M
+       fields []string
+}
+
+func (r redact) MarshalLogObject(enc zapcore.ObjectEncoder) error {
+       v, err := private.Redact(r.value, "", r.fields)
+       if err != nil {
+               return fmt.Errorf("could not redact value: %v", err)
+       }
+       return v.MarshalLogObject(enc)
+}
+
 func Plugin(log *logp.Logger, store inputcursor.StateStore) v2.Plugin {
        return v2.Plugin{
                Name:       inputName,
diff --git a/x-pack/filebeat/input/httpjson/request.go b/x-pack/filebeat/input/httpjson/request.go
index 6cc46b27f2..5dfb91dbdb 100644
--- a/x-pack/filebeat/input/httpjson/request.go
+++ b/x-pack/filebeat/input/httpjson/request.go
@@ -465,7 +465,7 @@ func (rf *requestFactory) newRequest(ctx *transformContext) (transformable, erro
                }
        }
 
-       rf.log.Debugf("new request: %#v", req)
+       rf.log.Debugw("new request", "req", redact{value: mapstr.M(req), fields: []string{"header.Authorization"}})
 
        return req, nil
 }

Could also be used in place of the current redactor in CEL, though that has a non-deletion redaction that this does not have. Adding that requires thought since this will redact non-string values.

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---

This is an automatic backport of pull request #40997 done by [Mergify](https://mergify.com).

[botelastic]

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[mergify]

This pull request has not been merged yet. Could you please review and merge it @efd6? 🙏